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

雙指標法，從相距最遠開始，既然我們要使得容積最大，肯定是要移動高度較小一點的指標；

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