trapping-rain-water

题目描述

 

Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it is able to trap after raining.

For example,
Given[0,1,0,2,1,0,1,3,2,1,2,1], return6.

The above elevation map is represented by array [0,1,0,2,1,0,1,3,2,1,2,1]. In this case, 6 units of rain water (blue section) are being trapped. Thanks Marcos for contributing this image!

---

class Solution {
public:
    int trap(int A[], int n) {
        int res = 0, l = 0, r = 0, maxIndex = 0;
        for(int i=0; i A[maxIndex])
                maxIndex = i;
        }
        for(int i=0; imaxIndex; i--){
            if(A[i] < r)
                res += (r - A[i]);
            else
                r = A[i];
        }
        return res;
    }
};