Trapping Rain Water

感觉和

Container With Most Water

 很像，这里有个问题，如果让球最大的坑，怎么做呢？

还有candy那道题，好像都是这种双扫系列的

ref http://fisherlei.blogspot.com/2013/01/leetcode-trapping-rain-water.html 双扫

public class Solution {

    public int trap(int[] A) {

        if(A==null || A.length<3) return 0;

        int res=0, curV = 0, max=A[0];

        int[] mL = new int[A.length];

        int[] mR = new int[A.length];

        

        for(int i=1; i<A.length-1; i++){

            mL[i] = max;

            max = Math.max(A[i],max);

        }

        max = A[A.length-1];

        for(int j=A.length-2; j>=0; j--){

            mR[j] =max;

            max = Math.max(A[j], max);

            curV = Math.min(mL[j], mR[j])-A[j];

            if(curV>0) 

                res += curV;

        }

        

        return res;

    }

}