Trapping Rain Water

Topic

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

For example,
Given [0,1,0,2,1,0,1,3,2,1,2,1] , return 6 .

Method

For each a[i],trap water is min (left, right)-a[i];

    public int Trap (int[] A) {        if (a = = NULL | | A.length = = 0 | | A.length = = 1 | | A.length = = 2) {            return 0;        }        int len = a.length;        Int[] left = new Int[len];        Int[] right = new Int[len];        int leftmax = 0;        for (int i = 0; i < len; i++) {        left[i] = Leftmax;        if (A[i] > Leftmax) {        Leftmax = A[i];        }        }        int rightmax = 0;        for (int i = len; i > 0; i--) {        right[i-1] = Rightmax;        if (A[i-1] > Rightmax) {        Rightmax = a[i-1];        }        }                int sum = 0;        for (int i = 0; i < len; i++) {        int temp = Math.min (Left[i], right[i])-a[i];        if (Temp > 0) {        sum + = temp;        }        }        return sum;    }

Trapping Rain Water