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) {
       int [][]arr=new int[m][n];
       for(int i=0;i<n;i++){
           arr[0][i]=1;
       }for(int i=0;i<m;i++){
           arr[i][0]=1;
       }
       for(int i=1;i<m;i++){
           for(int j=1;j<n;j++){
               arr[i][j]=arr[i-1][j]+arr[i][j-1];
           }
       }
       return arr[m-1][n-1];
    }
}