洛谷 P2756 飞行员配对方案问题

#include <cstring>
#include <cstdio>
#include <queue>
#define inf 1e9

using namespace std;

struct node
{
    int next,to,dis;
}e[100*100];
bool vis[1501];
queue<int>q;
int cur[1501],x[1501],num,deep[1501],Answer,S,T,head[100*100],tot=1,m,n;
void add_edge(int u,int v,int l)
{
    e[++tot].to=v;
    e[tot].next=head[u];
    e[tot].dis=l;
    head[u]=tot;
}
bool bfs(int s,int t)
{
    memset(vis,0,sizeof(vis));
    memset(deep,0x7f,sizeof(deep));
    while(!q.empty() )
    q.pop() ;
    for(int i=0;i<=T;++i)
    cur[i]=head[i];
    q.push(s);deep[s]=0;vis[s]=1;
    while(!q.empty() )
    {
        int Top=q.front() ;
        q.pop() ;
        vis[Top]=false;
        for(int i=head[Top];i!=-1;i=e[i].next)
        {
            int to=e[i].to;
            if(deep[to]>inf&&e[i].dis)
            {
                deep[to]=deep[Top]+1;
                if(!vis[to]) {q.push(to);vis[to]=1;} 
            }
        }
    }
    return deep[t]<inf;
}
int dfs(int now,int t,int limit)
{
    int i,f,rest=0;
    if(limit==0) return 0;
    if(now==t) return limit;
    for(i=head[now];i!=-1;i=e[i].next)
    {
        int To=e[i].to;
        if(deep[To]==deep[now]+1&&(f=dfs(To,t,min(e[i].dis,limit))))
        {
            if(f) x[now]=To;
            rest+=f;
            limit-=f;
            e[i].dis-=f;
            e[i^1].dis+=f;
            x[now]=To;
            if(!limit)
            break;
        }
    }
    return rest;
}
void dinic(int s,int t)
{
    while(bfs(s,t))
        Answer+=dfs(s,t,inf);
}
int main()
{
    scanf("%d%d",&m,&n);
    memset(head,-1,sizeof(head));
    S=0;T=n+1;
    for(int i=1;i<=m;++i) {add_edge(S,i,1);add_edge(i,S,0);} 
    for(int i=m+1;i<=n;++i) {add_edge(i,T,1);add_edge(T,i,0);} 
    int u,v;
    scanf("%d%d",&u,&v);
    while(u!=-1&&v!=-1)
    {
        add_edge(u,v,1);
        add_edge(v,u,0);
        scanf("%d%d",&u,&v);
    }
    dinic(S,T);
    if(Answer)
    {
        printf("%d\n",Answer);
        for(int i=1;i<=m;++i)
            if(x[i]) 
                printf("%d %d\n",i,x[i]);
    }
    else printf("No Solution!");
    return 0;
}