leetcode -- Trapping Rain Water

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], return 6.

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!

本题寻找当前index的最高左右边界，当前index可蓄水量=(min(left, right) - cur)

public class Solution {
    public int trap(int[] A) {
        // Start typing your Java solution below
        // DO NOT write main() function
        int len = A.length;
        int l = 0, r = 0;
        int result = 0;
        
        for(int i = 1; i < len - 1; i++){
            for(int m = 0; m < i; m ++){
                if(A[m] > l){
                    l = A[m];
                }            
            }
            
            for(int n = len - 1; n > i; n --){
                if(A[n] > r){
                    r = A[n];
                }
            }
            
            int min = Math.min(l, r);
            if(min - A[i] > 0){
                result += min - A[i];
            }
            l = 0;
            r = 0;
        }
        return result;
    }
}

 

ref:http://tech-wonderland.net/blog/leetcode-trapping-rain-water.html