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 MarcZ??http://www.2cto.com/kf/ware/vc/" target="_blank" class="keylink">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"brush:java;"> public static int trap(int[] A){ int len = A.length; if(len <= 2) return 0; int higest = A[0],high_index = 0; for(int i=0;i maxl) maxl = A[i]; else sum += maxl - A[i]; } for(int i=len-1;i>high_index;i--){ if(A[i] >maxr) maxr = A[i]; else sum += maxr-A[i]; } return sum; }