medium two pointers

11. Container With Most Water

Leetcode Diary

Posted by Xudong on July 7, 2020

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.

lc-11

Example:

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

Thoughts

设左右两个指针\(l\)和\(r\),从两侧向中间移动，扫描所有有可能大于当前最大值的长方形
因为向中间移动肯定会导致底部变短，所以每次移动要选择有可能使得高(high)变长的指针移动

Code(JAVA)

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