Container With Most Water

Given n non-negative integers a₁, a₂, ..., a_n, where each represents a point at coordinate (i, a_i). n vertical lines are drawn such that the two endpoints of line i is at (i, a_i) 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.

最简单的做法 ： 直接遍历。 O(n ^ 2)。

public class Solution {
    public int maxArea(int[] height) {
        // Note: The Solution object is instantiated only once and is reused by each test case.
        if(height == null || height.length == 0) return 0;
        int len = height.length;
        int max = Integer.MIN_VALUE;
        for(int i = 0; i < len; i ++){
            for(int j = i + 1; j < len; j ++){
                int sum = Math.min(height[i],height[j]) * (j - i);
                if(sum > max) max = sum;
            }
        }
        return max;
    }
}

超时。采用双指针来做。

public class Solution {
    public int maxArea(int[] height) {
        // Note: The Solution object is instantiated only once and is reused by each test case.
        if(height == null || height.length == 0) return 0;
        int len = height.length;
        int max = Integer.MIN_VALUE;
        int i = 0;
        int j = len - 1;
        while(i < j){
            int sum = Math.min(height[i],height[j]) * (j - i);
            if(sum > max) max = sum;
            if(height[i] < height[j]) i ++;
            else j --;
        }
        return max;
    }
}