[LeetCode] 11. Container With Most Water_Medium tag: 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 the line i is at (i, ai) and (i, 0). Find two lines, which, together with the x-axis forms a container, such that the container contains the most water.

Notice that you may not slant the container.

 

Example 1:

Input: height = [1,8,6,2,5,4,8,3,7]
Output: 49
Explanation: 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 2:

Input: height = [1,1]
Output: 1

Example 3:

Input: height = [4,3,2,1,4]
Output: 16

Example 4:

Input: height = [1,2,1]
Output: 2

 

Constraints:

• n == height.length
• 2 <= n <= 105
• 0 <= height[i] <= 104

 

Ideas:

    use two pointers, width = r - l, h = min(height[l], height[r]), height 小的那一方往中间移动。

 

Code:

class Solution:
    def maxArea(self, height: List[int]) -> int:
        ans, l, r = 0, 0, len(height) - 1
        while l < r:
            width = r - l
            if height[l] <= height[r]:
                h = height[l]
                l += 1
            else:
                h = height[r]
                r -= 1
            ans = max(ans, width * h)
        return ans