4

Author: kedebug

TrappingRainWater/TrappingRainWater.cpp

@@ -0,0 +1,26 @@
+class Solution {
+public:
+    int trap(int A[], int n) {
+        // Start typing your C/C++ solution below
+        // DO NOT write int main() function
+        
+        int max_from_left[n];
+        int max_from_right[n];
+        
+        max_from_left[0] = A[0];
+        for (int i = 1; i < n; i++)
+            max_from_left[i] = max(max_from_left[i-1], A[i]);
+        
+        max_from_right[n-1] = A[n-1];
+        for (int i = n - 2; i >= 0; i--)
+            max_from_right[i] = max(max_from_right[i+1], A[i]);
+            
+        int water = 0;
+        for (int i = 1; i < n - 1; i++) {
+            int min_height = min(max_from_left[i-1], max_from_right[i+1]);
+            if (min_height > A[i])
+                water += min_height - A[i];
+        }
+        return water;
+    }
+};