114 · 不同的路径Unique Paths

114 · 不同的路径Unique Paths

描述
A robot is located at the top-left corner of a m x nmxn 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.

How many possible unique paths are there?
Example 2:

Input:

n = 3
m = 3
Output:

6
Explanation:

D : Down
R : Right

DDRR
DRDR
DRRD
RRDD
RDRD
RDDR

public class Solution {
    /**
     * @param m: positive integer (1 <= m <= 100)
     * @param n: positive integer (1 <= n <= 100)
     * @return: An integer
     */
    public int uniquePaths(int m, int n) {
        // write your code here
         int[][] f = new int[m][n] ;
         for(int i = 0 ; i < m ; i++){
             for(int j = 0 ; j < n ; j++){
                 if(i == 0 || j == 0){
                     f[i][j] = 1 ;
                 }else{
                     f[i][j] = f[i-1][j] + f[i][j-1] ;
                 }
             }
         }
         return f[m-1][n-1] ;
    }
}