Problem

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 and n is at least 2.

Analysis

We can use double pointers to solve this problem, let left and right denote the index of left and right pointer respectively, then we have
– height[left] < height[right], left++
– height[left] >= height[right], right–

Solution

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