Unique Paths

A robot is located at the top-left corner of a m x n grid.
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?

Solution:
1. Use formula C(x,t) = t!/(x!*(t-x)!) (x should be large for calculation).
2. Dynamic programming. UP(i,j) = UP(i-1,j) + UP(i,j-1).

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