題目

You are given an integer array height of length n. There are n vertical lines drawn such that the two endpoints of the ith line are (i, 0) and (i, height[i]).

Find two lines that together with the x-axis form a container, such that the container contains the most water.

Return the maximum amount of water a container can store.

Notice that you may not slant the container.

題目連結

題目圖

Example 1

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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

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

解釋題目

height 是一個 integer array，每一個元素代表一個線段的高度。

任意兩條線段，沿著 X 軸方向，可以假想成一個容器，容器不能傾斜。

求容器最大能容納的水量。

思路

  1. Initial: 左指針指向最前面的 height，右指針指向最後面的 height。
  2. 開始計算水量，記錄最大水量。
  3. 若左邊的高度較矮，左指針就右移。若右邊的高度較矮，右指針就左移。移完指針後，回到第二步。
  4. 透過 Two Pointers，就能把所有狀況跑一遍。

程式碼

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class Solution {
public:
    int maxArea(vector<int>& height) {
        int result = 0;
        int left = 0;
        int right = height.size() - 1; 

        while(left < right){
            int area = (right - left) * min(height[left], height[right]);
            result = max(result, area);
            if(height[left] <= height[right])
                left++;
            else
                right--;
        }

        return result;
    }
};