Triangle java

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.

 

 

Example

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.

 

 

public class Solution {
    /**
     * @param triangle: a list of lists of integers.
     * @return: An integer, minimum path sum.
     */
    public int minimumTotal(int[][] triangle) {
        // write your code here
        if(triangle.length==0) return 0;
        int n=triangle.length;
        
        int[][] minSum=new int[n][n];
        
        for(int j=n-1;j>=0;j--)
        {
            for(int i=0;i<=j;i++)
            {
                if(j==n-1)
                {
                    minSum[j][i]=triangle[j][i];
                }
                else
                {
                    int a=minSum[j+1][i]+triangle[j][i];
                    int b=minSum[j+1][i+1]+triangle[j][i];
                    minSum[j][i]=Math.min(a,b);
                }
            }
        }
        return minSum[0][0];
        
    }
}