求一次最大流后，分别对所有满流的边的容量+1，然后看是否存在增广路。

1 #include
     
        2 #include
      
         3 #include
       
          4 #include
        
           5 using namespace std;  6 #define INF (1<<30)  7 #define MAXN 555   8 #define MAXM 11111   9  10 struct Edge{ 11     int v,cap,flow,next; 12 }edge[MAXM]; 13 int vs,vt,NE,NV; 14 int head[MAXN]; 15  16 void addEdge(int u,int v,int cap){ 17     edge[NE].v=v; edge[NE].cap=cap; edge[NE].flow=0; 18     edge[NE].next=head[u]; head[u]=NE++; 19     edge[NE].v=u; edge[NE].cap=0; edge[NE].flow=0; 20     edge[NE].next=head[v]; head[v]=NE++; 21 } 22  23 int level[MAXN]; 24 int gap[MAXN]; 25 void bfs(){ 26     memset(level,-1,sizeof(level)); 27     memset(gap,0,sizeof(gap)); 28     level[vt]=0; 29     gap[level[vt]]++; 30     queue
         
           que; 31     que.push(vt); 32     while(!que.empty()){ 33         int u=que.front(); que.pop(); 34         for(int i=head[u]; i!=-1; i=edge[i].next){ 35             int v=edge[i].v; 36             if(level[v]!=-1) continue; 37             level[v]=level[u]+1; 38             gap[level[v]]++; 39             que.push(v); 40         } 41     } 42 } 43  44 int pre[MAXN]; 45 int cur[MAXN]; 46 int ISAP(bool statue){ 47     bfs(); 48     memset(pre,-1,sizeof(pre)); 49     memcpy(cur,head,sizeof(head)); 50     int u=pre[vs]=vs,flow=0,aug=INF; 51     gap[0]=NV; 52     while(level[vs]