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LeetCode 42 Trapping Rain Water(积水体积)

题目链接: https://leetcode.com/problems/trapping-rain-water/?tab=Description
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Problem: 根据所给数组的值,按照上图的示意图。求解积水最大体积。
 
 
首先对所给数组进行遍历操作,求出最大高度所对应的下标为maxIndex
 
之后从左向右进行遍历,设置左边高度为leftMax 并初始化为 height[0],从i==1到i==maxIndex进行遍历。不断更新water,以及leftMax
    当height[I]小于leftMax时,water += leftMax - height
    当height[i]大于leftMax时,leftMax = height[I]
 
之后从i==height.length - 2到下标 I == maxIndex进行遍历操作 初始化rightMax = height[height.length-1]
    当height[I]小于rightMax时,water+=rightMax - height[I]
    当height[I]大于rightMax时,rightMax = height[I]
 
函数结果返回water
 
参考代码:
 
package leetcode_50;/*** *  * @author pengfei_zheng * 求积水的体积 */public class Solution42 {    public static int trap(int[] height) {        if (height.length <= 2) return 0;        int max = -1;        int maxIndex = 0;        for (int i = 0; i < height.length; i++) {            if (height[i] > max) {                max = height[i];                maxIndex = i;            }        }                int leftMax = height[0];        int water = 0;        for (int i = 1; i < maxIndex; i++) {            if (height[i] > leftMax) {                leftMax = height[i];            } else {                water += leftMax - height[i];            }        }                int rightMax = height[height.length - 1];        for (int i= height.length - 2; i > maxIndex; i--) {            if (height[i] > rightMax) {                rightMax = height[i];            } else {                water += rightMax - height[i];            }        }                return water;    }    public static void main(String[]args){//        int []height={0,1,0,2,1,0,1,3,2,1,2,1};        int []height={10,0,11,0,10};        System.out.println(trap(height));    }}

 

LeetCode 42 Trapping Rain Water(积水体积)