Leetcode-Unique Paths

http://oj.leetcode.com/problems/unique-paths/

题目描述

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?

Note: m and n will be at most 100.

AC代码

#include <iostream>
#include <cstdio>
#include <vector>

using namespace std;

int uniquePaths(int m, int n)
{
        vector<int> f(n, 0);
        f[0] = 1;
        for(int i = 0; i < m; i++)
        {
            for(int j = 1; j < n; j++)
            {
                //初始状体f[i][j], (1,1)->(i,j),f[i][j] = f[i-1][j] + f[i][j-1]
                f[j] = f[j - 1] + f[j];
            }
        }
        return f[n - 1];
}

int main()
{
        int m, n;

    #ifndef ok
        freopen("in3.in", "r", stdin);
        freopen("std3.out", "w", stdout);
    #endif

        while(cin>>m>>n)
            cout<<uniquePaths(m,n)<<endl;

    #ifndef ok
        fclose(stdin);
        fclose(stdout);
    #endif

        return 0;
}