hdu 3811 Permutation

Problem Description

In combinatorics a permutation of a set S with N elements is a listing of the elements of S in some order (each element occurring exactly once). There are N! permutations of a set which has N elements. For example, there are six permutations of the set {1,2,3}, namely [1,2,3], [1,3,2], [2,1,3], [2,3,1], [3,1,2], and [3,2,1].
But Bob think that some permutations are more beautiful than others. Bob write some pairs of integers(Ai, Bi) to distinguish beautiful permutations from ordinary ones. A permutation is considered beautiful if and only if for some i the Ai-th element of it is Bi. We want to know how many permutations of set {1, 2, ...., N} are beautiful.

 

Input

The first line contains an integer T indicating the number of test cases.
There are two integers N and M in the first line of each test case. M lines follow, the i-th line contains two integers Ai and Bi.

Technical Specification
1. 1 <= T <= 50
2. 1 <= N <= 17
3. 1 <= M <= N*N
4. 1 <= Ai, Bi <= N

 

Output

For each test case, output the case number first. Then output the number of beautiful permutations in a line.

 

Sample Input

3 3 2 1 1 2 1 3 2 1 1 2 2 4 3 1 1 1 2 1 3

 

Sample Output

Case 1: 4 Case 2: 3 Case 3: 18

 

Author

hanshuai

 

Source

The 6th Central China Invitational Programming Contest and 9th Wuhan University Programming Contest Preliminary

又是一题状态dp……当年比赛的时候RE到死没出来，今天1Y……rp咩？

#include 
#include 

int map[20][20];
long long dp[1<<18];
long long fact[18];

int main()
{
    int i,j,n,T,m,x,y,p,k,cnt;
    scanf("%d",&T);
    fact[0]=1;
    for (i=1;i<18;i++)
    {
        fact[i]=fact[i-1]*i;
    }
    cnt=1;
    while(T--)
    {
        scanf("%d%d",&n,&m);
        memset(map,0,sizeof(map));
        for (i=0;i=0;j--)
            {
                if (dp[j]==0) continue;
                for (k=0;k