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Problem:
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!C
Code:
public class Solution { public int trap(int[] A) { if (A == null || A.length == 0) { return 0; } int[] leftMost = new int[A.length]; int[] rightMost = new int[A.length]; leftMost[0] = A[0]; rightMost[A.length - 1] = A[A.length - 1]; for (int i = 1; i < A.length; i++) { leftMost[i] = Math.max(leftMost[i - 1], A[i]); } for (int i = A.length - 2; i >= 0; i--) { rightMost[i] = Math.max(rightMost[i + 1], A[i]); } int sum = 0; for (int i = 1; i < A.length - 1; i ++) { sum = sum + (Math.min(rightMost[i], leftMost[i]) - A[i]); } return sum; } }
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原文地址:http://blog.csdn.net/luckyseven7777/article/details/43907091