题目1451：不容易系列之一(递推算法)

题目链接：http://ac.jobdu.com/problem.php?pid=1451

详解链接：https://github.com/zpfbuaa/JobduInCPlusPlus

参考代码：

//
//  1451 不容易系列之一.cpp
//  Jobdu
//
//  Created by PengFei_Zheng on 24/04/2017.
//  Copyright © 2017 PengFei_Zheng. All rights reserved.
//
 
#include <stdio.h>
#include <iostream>
#include <algorithm>
#include <string.h>
#include <cmath>
#define MAX_SIZE 22
 
using namespace std;
 
int n;
long long a[MAX_SIZE];
 
int main(){
    while(scanf("%d",&n)!=EOF){
        a[1] = 0;
        a[2] = 1;
        for(int i = 3 ; i <= n ; i++){
            a[i]= (i-1)*a[i-1]+(i-1)*a[i-2];
        }
        printf("%lld\n",a[n]);
    }
    return 0;
}
/**************************************************************
    Problem: 1451
    User: zpfbuaa
    Language: C++
    Result: Accepted
    Time:0 ms
    Memory:1520 kb
****************************************************************/