BZOJ2718: [Violet 4]毕业旅行

 1 #include<cstdio>
 2 #include<cstdlib>
 3 #include<cmath>
 4 #include<cstring>
 5 #include<algorithm>
 6 #include<iostream>
 7 #include<vector>
 8 #include<map>
 9 #include<set>
10 #include<queue>
11 #define inf 1000000000
12 #define maxn 110
13 #define maxm 500+100
14 #define eps 1e-10
15 #define ll long long
16 #define pa pair<int,int>
17 using namespace std;
18 inline int read()
19 {
20     int x=0,f=1;char ch=getchar();
21     while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1;ch=getchar();}
22     while(ch>=‘0‘&&ch<=‘9‘){x=10*x+ch-‘0‘;ch=getchar();}
23     return x*f;
24 }
25 int p[maxn],n,m,f[maxn][maxn];
26 bool v[maxn];
27 bool find(int x)
28 {
29     for(int i=1;i<=n;i++)
30     if (f[x][i])
31      if(!v[i])
32      {
33          v[i]=1;
34          if(!p[i]||find(p[i]))
35          {
36              p[i]=x;
37              return 1;
38          }
39      }
40     return 0; 
41 }
42 int main()
43 {
44     freopen("input.txt","r",stdin);
45     freopen("output.txt","w",stdout);
46     n=read();m=read();
47     int x,y;
48     while(m--)x=read(),y=read(),f[x][y]=1;
49     for(int k=1;k<=n;k++)
50      for(int i=1;i<=n;i++)
51       for(int j=1;j<=n;j++)
52        f[i][j]=f[i][j]||(f[i][k]&&f[k][j]);
53     int ans=0;  
54     for(int i=1;i<=n;i++)
55      {
56          memset(v,0,sizeof(v));
57          if(find(i))ans++;
58      }   
59     printf("%d\n",n-ans);
60     return 0; 
61 }