bloomberg的題，估計真正的IT也不會考這么簡單的。

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