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.

思路：双指针枚举左右边界，每次选择较小的那个指针进行移动，因为只有较小的那个才可能使得总面积变大(矩形面积是最小的那个边决定的)。

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