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.

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


Solutions:

Two pointers: the one with lower height moves inside.

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