Refactored 3 solutions

varunu28 · varunu28 · commit aab42e8f45e3 · 2020-01-16T07:33:41.000-08:00
diff --git a/Easy/Height Checker.java b/Easy/Height Checker.java
@@ -1,15 +1,13 @@
 class Solution {
-    public int heightChecker(int[] heights) {
-        int[] copy = Arrays.copyOf(heights, heights.length);
-        Arrays.sort(copy);
-
-        int count = 0;
-        for (int i = 0; i < heights.length; i++) {
-            if (copy[i] != heights[i]) {
-                count++;
-            }
-        }
-
-        return count;
+  public int heightChecker(int[] heights) {
+    int[] copy = Arrays.copyOf(heights, heights.length);
+    Arrays.sort(copy);
+    int count = 0;
+    for (int i = 0; i < heights.length; i++) {
+      if (heights[i] != copy[i]) {
+        count++;
+      }
     }
+    return count;
+  }
 }
diff --git a/Easy/Number of 1 bits.java b/Easy/Number of 1 bits.java
@@ -1,15 +1,14 @@
 public class Solution {
-    // you need to treat n as an unsigned value
-    public int hammingWeight(int n) {
-        int count = 0;
-        for (int i=0; i<32; i++) {
-            if ((n & 1) == 1) {
-                count++;
-            }
-            
-            n = n >> 1;
-        }
-        
-        return count;
+  // you need to treat n as an unsigned value
+  public int hammingWeight(int n) {
+    int bits = 0;
+    int mask = 1;
+    for (int i = 0; i < 32; i++) {
+      if ((n & mask) != 0) {
+        bits++;
+      }
+      mask <<= 1;
     }
+    return bits;
+  }
 }
diff --git a/Medium/Number of Dice Rolls With Target Sum.java b/Medium/Number of Dice Rolls With Target Sum.java
@@ -1,23 +1,27 @@
 class Solution {
-    int MOD = 1000000007;
-    public int numRollsToTarget(int d, int f, int target) {
-        Integer[][] dp = new Integer[d + 1][target + 1];
-        return helper(d, f, target, dp);
+  Map<String, Integer> map = new HashMap<>();
+  final int MODULO = 1000000007;
+  public int numRollsToTarget(int d, int f, int target) {
+    if (d == 0 && target == 0) {
+      return 1;
     }
-    
-    private int helper(int d, int f, int target, Integer[][] dp) {
-        if (d == 0 || target <= 0) {
-            return d == target ? 1 : 0;
-        }
-        if (dp[d][target] != null) {
-            return dp[d][target];
-        }
-        
-        dp[d][target] = 0;
-        for (int i = 1; i <= f; i++) {
-            dp[d][target] = (dp[d][target] + helper(d - 1, f, target - i, dp)) % MOD; 
-        }
-        
-        return dp[d][target];
+    if (d == 0 || target == 0) {
+      return 0;
     }
+    String key = d + "|" + target;
+    if (map.containsKey(key)) {
+      return map.get(key);
+    }
+    int res = 0;
+    for (int i = 1; i <= f; i++) {
+      if (target >= i) {
+        res = (res + numRollsToTarget(d - 1, f, target - i)) % MODULO;
+      }
+      else {
+        break;
+      }
+    }
+    map.put(key, res);
+    return map.get(key);
+  }
 }
