https://leetcode.com/problems/container-with-most-water/

题目：

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.

 

思路：

考虑从边界向里缩减范围。最重要的是注意到，假设现在边界的height是a和b，那么想在内部有别的点能比a、b框成的体积大，那么这个点一定得比a、b中的最小者大。所以不断从边界height较小的点向内缩减，直到内部为空。

只需遍历数组一次，所以复杂度为O(n)。

 

AC代码：

1 class Solution { 2 public: 3     int maxArea(vector
     
      & height) { 4         int i,j,n=height.size(),a=0,b=n-1,contain=min(height[0],height[n-1])*(n-1); 5         while(a
      
       height[a]) 9                         break;10                 }11                 if(min(height[i],height[b])*(b-i)>contain){12                     contain=min(height[i],height[b])*(b-i);13                 }14                 a=i;15             }16             else{17                 for(j=b;j>a;j--){18                     if(height[j]>height[b])19                         break;20                 }21                 if(min(height[j],height[a])*(j-a)>contain){22                     contain=min(height[j],height[a])*(j-a);23                     }24                 b=j;25             }26         }27         return contain;28     }29 };