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Merge branch 'neetcode-gh:main' into main
2 parents 9fd4028 + d9d562f commit 26a3b0a

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‎cpp/102. Binary-Tree-Level-Order-Traversal.cpp

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/**
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* Definition for a binary tree node.
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* struct TreeNode {
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* int val;
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* TreeNode *left;
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* TreeNode *right;
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* TreeNode() : val(0), left(nullptr), right(nullptr) {}
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* TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
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* TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
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* };
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*/
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class Solution {
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public:
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vector<vector<int>> levelOrder(TreeNode* root) {
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queue< TreeNode* > q;
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q.push(root);
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vector<vector<int>> v;
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vector<int> k;
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TreeNode* c;
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int j;
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while(!q.empty() )
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{
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k.clear();
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j=q.size();
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for(int i=0;i<j;i++)
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{
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c=q.front();
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q.pop();
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if(c)
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{
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k.push_back(c->val);
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q.push(c->left);
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q.push(c->right);
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}
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}
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if(!k.empty())
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v.push_back(k);
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}
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return v;
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}
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};

‎cpp/11- Container with most water.cpp

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class Solution {
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public:
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int maxArea(vector<int>& height) {
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int i=0,j=height.size()-1;
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int maxA=0,minh;
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while(i<j)
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{
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minh=min(height[i],height[j]);
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if(minh*(j-i)>maxA)
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maxA=minh*(j-i);
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if(minh==height[i])
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i++;
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else
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j--;
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}
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return maxA;
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}
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};

‎cpp/110-Balanced-Binary-Tree.cpp

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/**
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* Definition for a binary tree node.
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* struct TreeNode {
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* int val;
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* TreeNode *left;
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* TreeNode *right;
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* TreeNode() : val(0), left(nullptr), right(nullptr) {}
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* TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
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* TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
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* };
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*/
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class Solution {
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public:
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int getHeight(TreeNode* root, unordered_map<TreeNode*, int>& umap) {
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if (root==NULL) return 0;
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if (umap.find(root) != umap.end()) return umap[root];
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int res = max(getHeight(root->left, umap), getHeight(root->right, umap))+1;
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umap[root] = res;
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return res;
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}
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bool isBalanced(TreeNode* root) {
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unordered_map<TreeNode*, int> umap;
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if (root == NULL) return true;
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if (abs(getHeight(root->left, umap) - getHeight(root->right, umap)) > 1) return false;
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return isBalanced(root->left) && isBalanced(root->right);
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}
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};

‎cpp/128-Longest-Consecutive-Sequence.cpp

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class Solution {
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public:
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int longestConsecutive(vector<int>& nums) {
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unordered_set<int> hs;
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for (int n : nums) {
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hs.insert(n);
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}
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int longest = 0;
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for (int n : nums) {
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// if n-1 is not in the set, the element can be the start of a sequence
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if (hs.find(n - 1) == hs.end()) {
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int length = 1;
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while (hs.find(n + length) != hs.end())
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++length;
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longest = max(longest, length);
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}
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}
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return longest;
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}
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};

‎cpp/136-Single-Number.cpp

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// Time complexity : O(n)
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// Space complexity : O(1)
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class Solution {
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public:
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int singleNumber(vector<int>& nums) {
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int res = 0;
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for(int num : nums){
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res^=num;
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}
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return res;
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}
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};

‎cpp/141-Linked-List-Cycle.cpp

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/**
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* Definition for singly-linked list.
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* struct ListNode {
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* int val;
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* ListNode *next;
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* ListNode(int x) : val(x), next(NULL) {}
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* };
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*/
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class Solution {
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public:
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bool hasCycle(ListNode *head) {
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if(!head) return 0;
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unordered_set<ListNode*> s;
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s.insert(head);
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ListNode * ptr=head->next;
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while(ptr)
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{
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if(s.find(ptr)==s.end())
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{
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s.insert(ptr);
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ptr=ptr->next;
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}
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else
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return 1;
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}
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return 0;
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}
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};

‎cpp/15-3Sum.cpp

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class Solution {
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public:
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vector<vector<int>> threeSum(vector<int>& nums) {
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sort(nums.begin(), nums.end());
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vector<vector<int>> res;
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for (int i = 0; i < nums.size(); ++i) {
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int a = nums[i];
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// triplet should not contain duplicate elements
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if (i > 0 && a == nums[i - 1])
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continue;
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// 2 ptr approach
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int l = i + 1, r = nums.size() - 1;
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while (l < r) {
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int threeSum = a + nums[l] + nums[r];
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if (threeSum > 0)
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r -= 1;
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else if (threeSum < 0)
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l += 1;
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else {
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// found triplet
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res.push_back({ a, nums[l], nums[r] });
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l += 1;
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// skip duplicates
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while (nums[l] == nums[l - 1] && l < r)
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l += 1;
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}
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}
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}
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return res;
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}
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};

‎cpp/155-Min-Stack.cpp

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using namespace std;
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class MinStack {
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public:
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stack<pair<int, int>> stk;
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int m;
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MinStack() {
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m = INT_MAX;
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}
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void push(int val) {
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stk.push({val, min(val, stk.empty()?INT_MAX:stk.top().second)});
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}
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void pop() {
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if(!stk.empty()) stk.pop();
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}
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int top() {
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return stk.top().first;
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}
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int getMin() {
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return stk.top().second;
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}
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};
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/**
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* Your MinStack object will be instantiated and called as such:
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* MinStack* obj = new MinStack();
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* obj->push(val);
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* obj->pop();
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* int param_3 = obj->top();
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* int param_4 = obj->getMin();
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*/

‎cpp/202-Happy-Number.cpp

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/*
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Time Complexity: O(log n)
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Space Complexity: O(log n)
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*/
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class Solution {
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public:
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bool isHappy(int n) {
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unordered_set<int> us;
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while (us.find(n) == us.end()) {
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us.insert(n);
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int temp = 0;
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while (n > 0) {
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int digit = n % 10;
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digit = digit * digit;
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temp += digit;
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n = n / 10;
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}
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n = temp;
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if (n == 1) {
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return true;
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}
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}
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return false;
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}
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};

‎cpp/238-Product-of-Array-Except-Self.cpp

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class Solution {
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public:
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vector<int> productExceptSelf(vector<int>& nums) {
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int n = nums.size();
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vector<int> res(n);
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// compute with prefix
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int prefix = 1;
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for (int i = 0; i < n; ++i) {
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res[i] = prefix;
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prefix *= nums[i];
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}
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// compute with posfix
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int postfix = 1;
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for (int i = n-1; i >= 0; --i) {
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res[i] *= postfix;
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postfix *= nums[i];
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}
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return res;
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}
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};

‎cpp/268-Missing-Number.cpp

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class Solution {
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public:
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int missingNumber(vector<int>& nums) {
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int sum=0;
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int n=nums.size();
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for(auto num: nums)
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sum+=num;
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return n*(n+1)/2 - sum;
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}
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};

‎cpp/3. Longest Substring Without Repeating Characters.cpp

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class Solution {
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public:
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int lengthOfLongestSubstring(string s) {
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if(s.length()==1)
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return 1;
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int j,max=0,count=0,found;
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string ss="";
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for(j=0;j<s.length();j++){
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found=ss.find(s[j]);
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if(found<0){
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count++;
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ss+=s[j];
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}else{
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ss.erase(0,found+1);
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ss+=s[j];
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count=ss.length();
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}
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max=std::max(max,count);
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}
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return max;
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}
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};

‎cpp/33-Search-in-Rotated-Sorted-Array.cpp

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// Time complexity: O(log(N))
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// Space complexity: O(1)
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class Solution {
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public:
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int search(vector<int>& nums, int target) {
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int start = 0, end = nums.size() - 1;
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while(start <= end){
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int mid = start + (end - start) / 2;
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if(nums[mid] == target)
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return mid;
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else if(nums[mid] >= nums[start]){
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if(target >= nums[start] && target < nums[mid])
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end = mid - 1;
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else
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start = mid + 1;
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}else{
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if(target > nums[mid] && target <= nums[end])
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start = mid + 1;
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else
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end = mid - 1;
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}
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}
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return -1;
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}
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};

‎cpp/347-Top-K-Frequent-Elements.cpp

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class Solution {
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public:
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vector<int> topKFrequent(vector<int>& nums, int k) {
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unordered_map<int, int> count;
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for (int n : nums) {
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++count[n];
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}
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vector<vector<int>> freq(nums.size() + 1, vector<int>());
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for (auto e : count) {
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freq[e.second].push_back(e.first);
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}
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vector<int> result;
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for (int i = freq.size()-1; i >= 0; --i) {
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for (int n : freq[i]) {
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result.push_back(n);
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if (result.size() == k)
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return result;
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}
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}
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return result;
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}
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};

‎cpp/36- Valid-Sudoku.cpp

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class Solution {
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public:
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bool isValidSudoku(vector<vector<char>>& board) {
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5+
unordered_set <int> row[9];
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unordered_set<int> col[9];
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unordered_set<int> squ[3][3];
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for(int i=0;i<9;i++)
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for(int j=0;j<9;j++)
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{
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if (board[i][j]=='.')
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continue;
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else if(row[i].find(board[i][j]) !=row[i].end()
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|| col[j].find(board[i][j]) !=col[j].end()
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|| squ[i/3][j/3].find(board[i][j]) !=squ[i/3][j/3].end()
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)
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return false;
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else
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{
21+
row[i].insert(board[i][j]);
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col[j].insert(board[i][j]);
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squ[i/3][j/3].insert(board[i][j]);
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}
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}
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return 1;}
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};

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