Leetcode 11. Container With Most Water (two pointers)

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

 

/*
   思路: 面积等于 width * min(height1, height2), 如果我们让width先最大，那么接下来就是缩小width, 虽然width 变小了, 但是height 可能会变大。
缩小width 的策略: 永远是缩小高度小的那一边,
*/
 
class Solution {
public:
    int maxArea(vector<int>& height) {
        int ans = 0;
        int le = 0, ri = height.size() - 1;
        while (le < ri) {
            ans = max(ans, min(height[le], height[ri]) * (ri - le));
            if (height[le] < height[ri]) {
                le++;
            }
            else {
                ri--;
            }
        }
        return ans;
    }
};