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;

    }

};