011_Container_With_Most_Water.cpp

/*
Descriprion:  
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.    
    
Example 1:  
Input: [1,8,6,2,5,4,8,3,7]
Output: 49
    
Hints:    
感觉这题非常 leetcode 的了。属于那种，可以很水(数据太弱)，但也可以不水的题目。  
我把这题归为区间类型的题目，气氛上就是找到某个满足条件的区间即可。
暴力 O(n2) 我试过了，数据太弱了也是随便过。显然这个区间在移动的时候有一些特殊的地方，这里说一个 O(n) 的思路，其实也很简单，首先我们设定头尾两个指针。发现，如果这个区间的头指针所在的高度比尾指针的大，显然我们希望尾指针向前移动；那么如果头指针所在的高度比尾指针的小，显然头指针应该向后走。
*/

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

        while (left < right) {
            int h;
            if(height[left]>height[right]) h = height[right];
            else h = height[left];
            
            contain = h * (right - left);
            if (contain > maxn) {
                maxn = contain;
            }
            
            if (height[left] < height[right]) left++;
            else right--;
        }

        return maxn;
    }
};