题目链接：http://acm.split.hdu.edu.cn/showproblem.php?pid=1151
题意：就是求最小路径覆盖，根据定义出的题。
1 /* 2 ━━━━━┒ギリギリ♂ eye！ 3 ┓┏┓┏┓┃キリキリ♂ mind！ 4 ┛┗┛┗┛┃＼○／ 5 ┓┏┓┏┓┃ / 6 ┛┗┛┗┛┃ノ) 7 ┓┏┓┏┓┃ 8 ┛┗┛┗┛┃ 9 ┓┏┓┏┓┃ 10 ┛┗┛┗┛┃ 11 ┓┏┓┏┓┃ 12 ┛┗┛┗┛┃ 13 ┓┏┓┏┓┃ 14 ┃┃┃┃┃┃ 15 ┻┻┻┻┻┻ 16 */ 17 #include <algorithm> 18 #include <iostream> 19 #include <iomanip> 20 #include <cstring> 21 #include <climits> 22 #include <complex> 23 #include <fstream> 24 #include <cassert> 25 #include <cstdio> 26 #include <bitset> 27 #include <vector> 28 #include <deque> 29 #include <queue> 30 #include <stack> 31 #include <ctime> 32 #include <set> 33 #include <map> 34 #include <cmath> 35 using namespace std; 36 #define fr first 37 #define sc second 38 #define cl clear 39 #define BUG puts("here!!!") 40 #define W(a) while(a--) 41 #define pb(a) push_back(a) 42 #define Rint(a) scanf("%d", &a) 43 #define Rs(a) scanf("%s", a) 44 #define Cin(a) cin >> a 45 #define FRead() freopen("in", "r", stdin) 46 #define FWrite() freopen("out", "w", stdout) 47 #define Rep(i, len) for(int i = 0; i < (len); i++) 48 #define For(i, a, len) for(int i = (a); i < (len); i++) 49 #define Cls(a) memset((a), 0, sizeof(a)) 50 #define Clr(a, x) memset((a), (x), sizeof(a)) 51 #define Full(a) memset((a), 0x7f7f7f, sizeof(a)) 52 #define lrt rt << 1 53 #define rrt rt << 1 | 1 54 #define pi 3.14159265359 55 #define RT return 56 #define lowbit(x) x & (-x) 57 #define onecnt(x) __builtin_popcount(x) 58 typedef long long LL; 59 typedef long double LD; 60 typedef unsigned long long ULL; 61 typedef pair<int, int> pii; 62 typedef pair<string, int> psi; 63 typedef pair<LL, LL> pll; 64 typedef map<string, int> msi; 65 typedef vector<int> vi; 66 typedef vector<LL> vl; 67 typedef vector<vl> vvl; 68 typedef vector<bool> vb; 69 70 const int maxn = 555; 71 int nu, nv; 72 int G[maxn][maxn]; 73 int linker[maxn]; 74 bool vis[maxn]; 75 76 bool dfs(int u) { 77 For(v, 1, nv+1) { 78 if(G[u][v] && !vis[v]) { 79 vis[v] = 1; 80 if(linker[v] == -1 || dfs(linker[v])) { 81 linker[v] = u; 82 return 1; 83 } 84 } 85 } 86 return 0; 87 } 88 89 int hungary() { 90 int ret = 0; 91 Clr(linker, -1); 92 For(u, 1, nu+1) { 93 Cls(vis); 94 if(dfs(u)) ret++; 95 } 96 return ret; 97 } 98 99 int n, m; 100 101 int main() { 102 // FRead(); 103 int T, u, v; 104 Rint(T); 105 W(T) { 106 Cls(G); 107 Rint(n); Rint(m); 108 nu = nv = n; 109 Rep(i, m) { 110 Rint(u); Rint(v); 111 G[u][v] = 1; 112 } 113 printf("%d ", nu - hungary()); 114 } 115 RT 0; 116 }