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.

题目要求：求包含的面积,用两个指针l和r，初始化分别指向数组的两端，然后在向中间移动找到最大容量。如果l指向的数字小，则l需要右移才有可能获得更大容量，因为此时如果左移r，得到的容量肯定比左移r之前的容量小（高度已经被较小的l限制住了）。如果r指向的数字小，则需要左移r。这样，当l和r相遇的时候，最大的容量就是我们需要的。

时间复杂度：O(n)

空间复杂度：O(1)

class Solution {
public:
    int maxArea(vector<int>& height) 
    {
        int left = 0, right = height.size() - 1;
        int ret = 0;
        while (left < right)
        {
            int lowhigh = min(height[left], height[right]);
            ret = max(ret, lowhigh * (right - left));
            if (height[left] == lowhigh)
                left ++;
            else
                right --;
        }
        return ret;
    }
};