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.

class Solution {
public:
    int minimumTotal(vector<vector<int> > &triangle) 
    {
        int n=triangle.size();
        if(n==0) return 0;
        
        int minpath1[n];
        int minpath2[n];
        
        minpath1[0]=triangle[0][0];
        int* min1=minpath1;
        int* min2;
        
        for(int i=1;i<n;i++)
        {
            if(min1==minpath1)
                min2=minpath2;
            else
                min2=minpath1;
                
            min2[0]=min1[0]+triangle[i][0];
            min2[i]=min1[i-1]+triangle[i][i];
            
            for(int j=1;j<i;j++)
            {
                int sum1=min1[j]+triangle[i][j];
                int sum2=min1[j-1]+triangle[i][j];
                min2[j]=sum1;
                if(sum2<sum1) min2[j]=sum2;
            }
            
            min1=min2;
        }
        int minvalue=min1[0];
        for(int i=1;i<n;i++)
            if(min1[i]<minvalue)
                minvalue=min1[i];
            
        return minvalue;
    }
};