【题目链接】
无法匹配的时候break就好了。
/* Pigonometry */ #include <cstdio> #include <algorithm> using namespace std; const int maxn = 1005; int n, m, head[maxn], cnt, from[maxn], vis[maxn], clo; struct _edge { int v, next; } g[maxn << 1]; inline int iread() { int f = 1, x = 0; char ch = getchar(); for(; ch < '0' || ch > '9'; ch = getchar()) f = ch == '-' ? -1 : 1; for(; ch >= '0' && ch <= '9'; ch = getchar()) x = x * 10 + ch - '0'; return f * x; } inline void add(int u, int v) { g[cnt] = (_edge){v, head[u]}; head[u] = cnt++; } inline bool hungary(int x) { for(int i = head[x]; ~i; i = g[i].next) if(vis[g[i].v] != clo) { vis[g[i].v] = clo; if(!from[g[i].v] || hungary(from[g[i].v])) { from[g[i].v] = x; return 1; } } return 0; } int main() { n = iread(); m = iread(); for(int i = 1; i <= n; i++) head[i] = -1; cnt = 0; for(int i = 1; i <= m; i++) { int a = iread(), b = iread(); a++; b++; add(i, a); if(a ^ b) add(i, b); } int ans = 0; for(int i = 1; i <= m; i++) { clo++; if(hungary(i)) ans++; else break; } printf("%d\n", ans); return 0; }