最小顶点覆盖:用最少的点,让每条边都至少和其中一个点关联;
。。。以为自己很聪明。。用边连边。。。最后还是点连点 哎。。。。
hc 写的 匈牙利足够/////
#include <iostream> #include <cstdio> #include <cstring> #include <queue> #include <algorithm> #include <cmath> #include <vector> #define mem(a, b) memset(a, b, sizeof(a)) using namespace std; const int maxn = 10010, INF = 0x7fffffff; int dx[maxn], dy[maxn], cx[maxn], cy[maxn], used[maxn]; int nx, ny, dis, n; vector<int> G[maxn]; int bfs() { queue<int> Q; dis = INF; mem(dx, -1); mem(dy, -1); for(int i=0; i<=nx; i++) { if(cx[i] == -1) { Q.push(i); dx[i] = 0; } } while(!Q.empty()) { int u = Q.front(); Q.pop(); if(dx[u] > dis) break; for(int v=0; v<G[u].size(); v++) { int i = G[u][v]; if(dy[i] == -1) { dy[i] = dx[u] + 1; if(cy[i] == -1) dis = dy[i]; else { dx[cy[i]] = dy[i] + 1; Q.push(cy[i]); } } } } return dis != INF; } int dfs(int u) { for(int v=0; v<G[u].size(); v++) { int i = G[u][v]; if(!used[i] && dy[i] == dx[u] + 1) { used[i] = 1; if(cy[i] != -1 && dis == dy[i]) continue; if(cy[i] == -1 || dfs(cy[i])) { cy[i] = u; cx[u] = i; return 1; } } } return 0; } int hk() { int res = 0; mem(cx, -1); mem(cy, -1); while(bfs()) { mem(used, 0); for(int i=0; i<=nx; i++) { if(cx[i] == -1 && dfs(i)) res++; } } return res; } int main() { while(cin>> n) { for(int i=0; i<maxn; i++) G[i].clear(); for(int i=0; i<n; i++) { int u, m; scanf("%d:(%d)",&u, &m); for(int j=0; j<m; j++) { int v; scanf("%d",&v); G[u].push_back(v); G[v].push_back(u); } } nx = ny = n-1; // cout<< rt<< " " << nx << " " <<endl; cout<< hk()/2 <<endl; } return 0; }