Triangle

Given a triangle, find the minimum path sum from top to bottom. Each step you may move to adjacent numbers on the row below.

For example, given the following triangle

[     [2],    [3,4],   [6,5,7],  [4,1,8,3]]

 

The minimum path sum from top to bottom is 11 (i.e., 2 + 3 + 5 + 1 = 11).

Note:

Bonus point if you are able to do this using only O(n) extra space, where n is the total number of rows in the triangle.

 

 

使用bottom-up方法将最小值汇聚到root，将中间结果保存在开辟的空间curMin中。

class Solution {public:    int minimumTotal(vector
     
      
        > &triangle) {        int m = triangle.size();        if(m == 0)            return 0;        else if(m == 1)            return triangle[0][0];                    vector
       
         curMin = triangle[m-1];        for(int i = m-2; i >= 0; i --)        {
    // for level i            for(int j = 0; j <= i; j ++)            {                curMin[j] = triangle[i][j] + min(curMin[j], curMin[j+1]);            }        }        return curMin[0];    }};