LeetCode-Unique Paths

作者：disappearedgod

文章出处：http://blog.csdn.net/disappearedgod/article/details/30244919

时间：2014-6-12

题目

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.

解法

DP解法

public class Solution {    public int uniquePaths(int m, int n) {        if(m==0||n==0)            return 0;        if(n==1||m==1)            return 1;        int[][] r = new int[m][n];        r[m-1][n-1] = 1;        for(int i = m-1 ; i >= 0 ; i--){            for(int j = n-1; j >= 0; j--){                if(i>0)                    r[i-1][j] += r[i][j];                 if(j>0)                    r[i][j-1] += r[i][j];            }        }        return r[0][1]+r[1][0];    }}