42. Trapping Rain Water

Author: FeiCoding

(#42)TrappingRainWater/TrappingRainWater.java

@@ -0,0 +1,21 @@
+class Solution {
+    public int trap(int[] height) {
+        int left = 0, right = height.length - 1;
+        int leftmax = 0, rightmax = 0;
+        int ans = 0;
+        while(left < right){
+            if(height[left] < height[right]){
+                if(height[left] >= leftmax) 
+                    leftmax = height[left];
+                else ans += leftmax - height[left];
+                left++;
+            }else{
+                if(height[right] >= rightmax)  
+                    rightmax = height[right];
+                else ans += rightmax - height[right];
+                right--;
+            }
+        }
+        return ans;
+    }
+}