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andyalgorithmandyalgorithm
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2023.01.05 andy-pc commit leetcode
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‎leetcode/src/main/java/AreNumbersAscending.java

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/**
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* 2042 检查句子中的数字是否递增
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*/
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public class AreNumbersAscending {
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public boolean areNumbersAscending(String s) {
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int pre = 0, cur;
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int left=0, right=0;
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while(left<s.length()){
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char c = s.charAt(left);
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if(('0'<=c && c<='9') && ((left==0) ||
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(s.charAt(left-1)<'0' || s.charAt(left-1)>'9'))){
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right = left+1;
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while(right<s.length()){
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char t = s.charAt(right);
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if(t<'0' || t>'9'){
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break;
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}else{
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right++;
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}
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}
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cur = Integer.parseInt(s.substring(left, right));
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if(cur<=pre){
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return false;
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}else{
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pre = cur;
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left = right;
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}
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}else{
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left++;
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}
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}
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return true;
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}
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}

‎leetcode/src/main/java/ArrayStringsAreEqual.java

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/**
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* 1662 检查两个字符串是否相等
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*/
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public class ArrayStringsAreEqual {
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public boolean arrayStringsAreEqual(String[] word1, String[] word2) {
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int r1=0,c1=0,r2=0,c2=0;
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while (r1<word1.length && r2<word2.length){
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if(word1[r1].charAt(c1)!=word2[r2].charAt(c2)) {
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return false;
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}
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c1++;
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c2++;
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if(c1==word1[r1].length()){
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r1++;
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c1=0;
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}
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if(c2==word2[r2].length()){
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r2++;
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c2=0;
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}
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}
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if(r1==word1.length && r2==word2.length && c1==0 && c2==0){
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return true;
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}else {
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return false;
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}
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}
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}

‎leetcode/src/main/java/ArrayStringsAreEqualRedoI.java

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/**
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* 1662 检查两个字符串是否相等
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*/
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public class ArrayStringsAreEqualRedoI {
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public boolean arrayStringsAreEqual(String[] word1, String[] word2) {
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int row1=0,col1=0;
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int row2=0,col2=0;
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while(row1<word1.length && row2<word2.length){
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if(col1==word1[row1].length() || col2==word2[row2].length()){
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if(col1==word1[row1].length()){
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row1++;
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col1=0;
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}
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if(col2==word2[row2].length()){
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row2++;
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col2=0;
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}
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}else if(word1[row1].charAt(col1)!=word2[row2].charAt(col2)){
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return false;
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}else{
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col1++;
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col2++;
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}
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}
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if(row1==word1.length && row2==word2.length){
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return true;
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}else{
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return false;
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}
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}
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}

‎leetcode/src/main/java/BuildTree.java

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import java.util.HashMap;
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/**
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* 105 重建二叉树
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*/
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public class BuildTree {
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public TreeNode buildTree(int[] preorder, int[] inorder) {
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if(preorder.length!=inorder.length || preorder.length==0){
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return null;
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}
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HashMap<Integer, Integer> map = new HashMap<>();
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for(int i=0; i<inorder.length; i++){
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map.put(inorder[i], i);
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}
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TreeNode root = dp(0, 0, inorder.length-1, preorder, map);
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return root;
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}
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TreeNode dp(int pos, int left, int right, int[] preorder, HashMap<Integer, Integer> map){
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// 递归终止
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if(left>right){
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return null;
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}
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// 建立根节点
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TreeNode node = new TreeNode(preorder[pos]);
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// 划分根节点、左子树、右子树
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int i = map.get(preorder[pos]);
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// 开启左子树递归
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node.left = dp(pos+1, left, i-1, preorder, map);
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// 开启右子树递归
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node.right = dp(pos+i-left+1, i+1, right, preorder, map);
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return node;
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}
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}

‎leetcode/src/main/java/CanJump.java

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/**
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* 55 跳跃游戏
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*/
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public class CanJump {
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public boolean canJump(int[] nums) {
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boolean res = true;
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int k = 0;
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for(int i=0; i<nums.length; i++) {
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if(i>k) {
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return false;
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}
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k = Math.max(k, i+nums[i]);
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}
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return res;
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}
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}

‎leetcode/src/main/java/CheckInclusion.java

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import java.util.HashMap;
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/**
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* 567. 字符串的排列
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*/
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public class CheckInclusion {
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public boolean checkInclusion(String s1, String s2) {
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int count = 0;
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int left=0, right=0;
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HashMap<Character, Integer> map1 = new HashMap<>();
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HashMap<Character, Integer> map2 = new HashMap<>();
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for(int i=0; i<s1.length(); i++){
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char c1 = s1.charAt(i);
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map1.put(c1, map1.getOrDefault(c1, 0)+1);
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}
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for(int i=0; i<s1.length(); i++){
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char c = s2.charAt(i);
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map2.put(c, map2.getOrDefault(c, 0)+1);
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if(map2.get(c)<=map1.getOrDefault(c,0)){
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count++;
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}
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right++;
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}
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if(count==s1.length()){
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return true;
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}
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while(right<s2.length()){
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char c1 = s2.charAt(left);
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char c2 = s2.charAt(right);
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map2.put(c2, map2.getOrDefault(c2, 0)+1);
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if(map2.get(c2)<=map1.getOrDefault(c2, 0)){
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count++;
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}
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map2.put(c1, map2.get(c1)-1);
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if(map2.get(c1)<map1.getOrDefault(c1, 0)){
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count--;
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}
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left++;
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right++;
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if(count==s1.length()){
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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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}

‎leetcode/src/main/java/CheckOnesSegment.java

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import java.util.Stack;
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/**
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* 1784. 检查二进制字符串字段
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*/
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public class CheckOnesSegment {
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public boolean checkOnesSegment(String s) {
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boolean res = true;
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Stack<Character> stack = new Stack<>();
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for(char c: s.toCharArray()){
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if(stack.isEmpty()){
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stack.push(c);
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}else{
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if(stack.peek()==c){
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continue;
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}else if(stack.size()==1){
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stack.push(c);
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}else if(stack.size()>1 && stack.peek()!=c){
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return false;
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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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}

‎leetcode/src/main/java/CombinationSum.java

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import java.util.ArrayList;
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import java.util.List;
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/**
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* 39. 数组总和
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*/
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public class CombinationSum {
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public List<List<Integer>> combinationSum(int[] candidates, int target) {
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List<List<Integer>> res = new ArrayList<>();
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dp(0, candidates, target, new ArrayList<Integer>(), res);
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return res;
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}
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void dp(int start, int[] candidates, int target, ArrayList<Integer> temp, List<List<Integer>> res){
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if(target==0){
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res.add(new ArrayList<>(temp));
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}else if(target<0){
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return;
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}
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for(int i=start; i<candidates.length; i++){
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temp.add(candidates[i]);
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dp(i, candidates, target-candidates[i], temp, res);
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temp.remove(temp.size()-1);
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}
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}
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}

‎leetcode/src/main/java/CombinationSum2.java

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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.List;
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/**
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* 39. 数组总和
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*/
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public class CombinationSum2 {
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public List<List<Integer>> combinationSum2(int[] candidates, int target) {
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List<List<Integer>> res = new ArrayList<>();
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Arrays.sort(candidates); // 从小到大排序
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dp(0, candidates, target, new ArrayList<Integer>(), res);
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return res;
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}
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void dp(int start, int[] candidates, int target, ArrayList<Integer> temp, List<List<Integer>> res){
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if(target==0){
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res.add(new ArrayList<>(temp));
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}else if(target<0){
22+
return;
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}
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for(int i=start; i<candidates.length; i++){
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// 枝剪去重
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if(i>start && candidates[i]==candidates[i-1]){
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continue;
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}
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temp.add(candidates[i]);
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dp(i+1, candidates, target-candidates[i], temp, res);
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temp.remove(temp.size()-1);
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}
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}
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}

‎leetcode/src/main/java/Combine.java

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import java.util.ArrayList;
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import java.util.List;
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/**
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* 77. 组合
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*/
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public class Combine {
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public List<List<Integer>> combine(int n, int k) {
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List<List<Integer>> res = new ArrayList<>();
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backtrack(k, 1, n, new ArrayList<Integer>(), res);
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return res;
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}
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void backtrack(int k, int start, int n, List<Integer> temp, List<List<Integer>> res){
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if(k==0){
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res.add(new ArrayList<>(temp));
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}
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for(int i=start; i<=n; i++){
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temp.add(i);
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backtrack(k-1, i+1, n, temp, res);
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temp.remove(temp.size()-1);
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}
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}
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}

‎leetcode/src/main/java/CommonChars.java

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import java.util.ArrayList;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Map;
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/**
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* 1002. 查找共用字符
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*/
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public class CommonChars {
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public List<String> commonChars(String[] words) {
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HashMap<Character, Integer> map = new HashMap<>();
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HashMap<Character, Integer> temp = new HashMap<>();
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List<String> res = new ArrayList<>();
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for(char c: words[0].toCharArray()){
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temp.put(c, temp.getOrDefault(c, 0)+1);
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}
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for(int i=1; i<words.length; i++){
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map = temp;
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temp = new HashMap<>();
21+
for(char c: words[i].toCharArray()){
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if(map.getOrDefault(c, 0)>0){
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map.put(c, map.get(c)-1);
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temp.put(c, temp.getOrDefault(c, 0)+1);
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}
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}
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}
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for(Map.Entry<Character, Integer> t: temp.entrySet()){
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for(int i=0; i<t.getValue(); i++){
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res.add(t.getKey().toString());
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}
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}
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return res;
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}
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}

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