[leetcode]Unique Paths

动态规划。巧妙的是通过在最上和最左边加一条0的线，大大简化了编程实现。

public class Solution {

    public int uniquePaths(int m, int n) {

        // Start typing your Java solution below

        // DO NOT write main() function

        int[][] mx = new int[m+1][n+1];

        

        for (int i = 0; i < m+1; i++) {

            mx[i][0] = 0;

        }

        for (int i = 0; i < n+1; i++) {

            mx[0][i] = 0;

        }



        for (int i = 1; i < m+1; i++) {

            for (int j = 1; j < n+1; j++) {

                if (i == 1 && j == 1) mx[i][j] = 1;

                else mx[i][j] = mx[i-1][j] + mx[i][j-1];

            }

        }

        

        return mx[m][n];

    }

}