java-Trapping Rain Water

标签：two points   array   

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!

从两边往中间进行搜索 首先找出最大值 再从头尾分别向最大值靠近 这样能保证只要内测高度小于仅次于它的外侧高度 必然能容纳 外高-内高 的水量 代码如下：

public class Solution {
    public  int trap(int[] A) {
		if(A.length<=2)return 0;
		int res=0;
		int max=A[0];
		int j=0;
		for(int i=1;i<A.length;i++){
			if(A[i]>max){
				max=A[i];
				j=i;
			}
		}
		int lmax=A[0];
		for(int m=1;m<j;m++){
			if(A[m]<lmax){
				res+=lmax-A[m];
			}else{
				lmax=A[m];
			}
		}
		int rmax=A[A.length-1];
		for(int n=A.length-1;n>j;n--){
			if(A[n]<rmax){
				res+=rmax-A[n];
			}else{
				rmax=A[n];
			}
		}
		return res;
	}
}

java-Trapping Rain Water

标签：two points   array   

原文地址：http://blog.csdn.net/u012734829/article/details/44199949