Unique Paths

easy one;

A robot is located at the top-left corner of a m x ngrid (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?

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

python

class Solution:    # @return an integer    def uniquePaths(self, m, n):        if m==0 or n==0:            return 0                    all = [[0]*n for i in range(m)]        for i in range(n):            all[0][i] = 1        for i in range(1,m):            all[i][0] = 1                for i in range(1,m):            for j in range(1,n):                all[i][j] = all[i-1][j] + all[i][j-1]                return all[m-1][n-1]