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!
本题寻找当前index的最高左右边界,当前index可蓄水量=(min(left, right) - cur)
1 public class Solution { 2 public int trap(int[] A) { 3 // Start typing your Java solution below 4 // DO NOT write main() function 5 int len = A.length; 6 int l = 0, r = 0; 7 int result = 0; 8 9 for(int i = 1; i < len - 1; i++){ 10 for(int m = 0; m < i; m ++){ 11 if(A[m] > l){ 12 l = A[m]; 13 } 14 } 15 16 for(int n = len - 1; n > i; n --){ 17 if(A[n] > r){ 18 r = A[n]; 19 } 20 } 21 22 int min = Math.min(l, r); 23 if(min - A[i] > 0){ 24 result += min - A[i]; 25 } 26 l = 0; 27 r = 0; 28 } 29 return result; 30 } 31 }
ref:http://tech-wonderland.net/blog/leetcode-trapping-rain-water.html