LeetCode Unique Paths

A robot is located at the top-left corner of a m x n grid (marked 'Start' in the diagram below).

The robot can only move either down or right at any point in time. The robot is trying to reach the bottom-right corner of the grid (marked 'Finish' in the diagram below).

How many possible unique paths are there?

Above is a 3 x 7 grid. How many possible unique paths are there?

Note: m and n will be at most 100.

public class Solution {
    public int uniquePaths(int m, int n) {
                if(m<=0||n<=0)
			return 0;
		if(m==1&&n==1)
			return 1;
		int[][] f=new int[m+1][n+1];
		for(int i=1;i<=m;i++)
			f[i][1]=1;
		for(int i=1;i<=n;i++)
			f[1][i]=1;
		for(int i=2;i<=m;i++)
			for(int j=2;j<=n;j++)
			{
				f[i][j]=f[i-1][j]+f[i][j-1];
			}
		return f[m][n];
    }
}