POJ1422 Air Raid

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstdlib>
 4 #include <cstring>
 5 
 6 inline void read(int &x)
 7 {
 8     x = 0;char ch = getchar(), c = ch;
 9     while(ch < ‘0‘ || ch > ‘9‘)c = ch, ch = getchar();
10     while(ch <= ‘9‘ && ch >= ‘0‘)x = x * 10 + ch - ‘0‘, ch = getchar();
11     if(c == ‘-‘)x = -x;
12 }
13 
14 const int INF = 0x3f3f3f3f;
15 
16 struct Edge
17 {
18     int u,v,next;
19     Edge(int _u, int _v, int _next){u = _u, v = _v, next = _next;}
20     Edge(){}
21 }edge[100000];
22 
23 int head[10000], cnt;
24 
25 inline void insert(int a, int b)
26 {
27     edge[++cnt] = Edge(a,b,head[a]);
28     head[a] = cnt;
29 }
30 
31 int n,m,lk[10000],b[10000];
32 
33 int dfs(int u)
34 {
35     for(register int pos = head[u];pos;pos = edge[pos].next)
36     {
37         int v = edge[pos].v;
38         if(b[v])continue;
39         b[v] = 1;
40         if(lk[v] == -1 || dfs(lk[v]))
41         {
42             lk[v] = u;
43             return 1;
44         }
45     }
46     return 0;
47 }
48 
49 int xiongyali()
50 {
51     int ans = 0;
52     memset(lk, -1, sizeof(lk));
53     for(register int i = 1;i <= n;++ i)
54     {
55         memset(b, 0, sizeof(b));
56         ans += dfs(i);
57     }
58     return ans;
59 }
60 
61 int t;
62 
63 int main()
64 {
65     read(t);
66     for(;t;--t)
67     {
68         memset(edge, 0, sizeof(edge));
69         memset(head, 0, sizeof(head));
70         cnt = 0;
71         read(n), read(m);
72         register int tmp1,tmp2,i;
73         for(i = 1;i <= m;++ i)
74         {
75             read(tmp1), read(tmp2);
76             insert(tmp1, tmp2);
77         }
78         printf("%d\n", n - xiongyali());
79     }
80     return 0;
81 }