Trapping Rain WaterMar 10 '124164 / 10550
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
这题之前面试时遇到过类似的。
但是是二维的情况,当时想得比较混乱。后来网上看到了不错的做法:从边界开始,每次取边界上最矮的板作为往里面floodfill,遇到高的停止。
这题类似的处理,简单很多。
二维:http://www.cnblogs.com/liangfeng/archive/2011/09/19/2181695.html
class Solution { public: int trap(int A[], int n) { int i = 0, j = n - 1, res = 0, cur; int *a = A; while (i < j) { if (a[i] < a[j]) { cur = i+1; while (cur <= j && a[cur] <= a[i]) res += a[i] - a[cur++]; i = cur; } else { cur = j - 1; while (cur >= i && a[cur] <= a[j]) res += a[j] - a[cur--]; j = cur; } } return res; } };