[LeetCode] 62. 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) {
        if(0 == m || 0 == n)
            return 0;
            
        int[] dp = new int[m];
        
        for(int i = 0; i < m; ++i){
            dp[i] = 1;
        }
        
        for(int i = 1; i < n; ++i){
            for(int j = 1; j < m; ++j){
                dp[j] += dp[j-1];
            }
        }
        
        return dp[m-1];
    }
}