leetcode 11. Container With Most Water

Given n non-negative integers a1, a2, ..., an , where each represents a point at coordinate (i, ai). n vertical lines are drawn such that the two endpoints of line i is at (i, ai) and (i, 0). Find two lines, which together with x-axis forms a container, such that the container contains the most water.

Note: You may not slant the container and n is at least 2.

 

The above vertical lines are represented by array [1,8,6,2,5,4,8,3,7]. In this case, the max area of water (blue section) the container can contain is 49.

 

Example:

Input: [1,8,6,2,5,4,8,3,7]
Output: 49

 

解法一：BF

 

解法二：two pointer

用两个指针在一头一尾，逐渐向中间夹紧。移动两边当中较短的那条边。因为如果移动较长的那条边必定会使得移动后的面积减小，所以移动短边可确保每一次move都是better one。

class Solution {
    public int maxArea(int[] height) {
        int max = 0;
        int i = 0, j = height.length-1;
        while(i<j){
            max = Math.max(max,Math.min(height[i],height[j])*(j-i));
            if(height[i]<height[j]) {
                i++;
            }else{
                j--;
            }
        }
        
        return max;
    }
}