Unique Paths - LeetCode

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?

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