POJ 1966 Cable TV Network

Description:

Given an undirected graph, ask at least how many points are removed to make the diagram disconnected. Points n≤50

Idea: First fix a point s, then enumerate another point T, and then ask for at least a few points to cut off to make two point not connected

Natural contact to the smallest cut, but the smallest cut is cut edge, cut point? As long as each point is split into two points, cutting a point is equivalent to disconnecting the edge in the middle of the two points it splits in the network.

So the Benquan in the original graph is set to positive infinity, then the Benquan between each point pair is set to 1, then you can use the minimum cut to write

#include <iostream>#include<cstring>#include<queue>#include<cstdio>using namespacestd;Const intN = the;Const intM =10010;Const intINF =1e9;intHead[n],now;structedges{intTo,next,w;} Edge[m<<1];voidAddintUintVintW) {Edge[++now] = {v,head[u],w}; Head[u] =Now ;}intN,m,s,t,dep[n],ans;voidinit () {memset (Edge,0,sizeof(Edge)); now =1; memset (Head,0,sizeof(head)); memset (DEP,0,sizeof(DEP));}intDinic (intXintflow) {    if(x = = t)returnflow; intRest =flow, K;  for(inti = head[x]; I i =Edge[i].next) {        intv =edge[i].to; if(EDGE[I].W && dep[v] = = Dep[x] +1) {k=Dinic (V,min (rest, EDGE[I].W)); if(!k) Dep[v] =0; EDGE[I].W-=K; Edge[i^1].W + =K; Rest-=K; }    }    returnFlow-rest;}BOOLBFs () {memset (DEP,0,sizeof(DEP)); Queue<int>Q; Q.push (s); Dep[s]=1;  while(!Q.empty ()) {        intx =Q.front (); Q.pop ();  for(inti = head[x]; I i =Edge[i].next) {            intv =edge[i].to; if(EDGE[I].W &&!)Dep[v])                {Q.push (v); DEP[V]= Dep[x] +1; if(v = = t)return 1; }        }    }    return 0;}structinput{intx, y;} INP[M];intMain () { while(SCANF ("%d%d", &n,&m)! =EOF) {ans=INF; intx, y;  for(inti =1; I <= m; i++) {scanf ("(%d,%d)",&x,&y); X+ +, y++; Inp[i]={x, y};//Add (X,y+n,inf); add (y+n,x,0);        }        if(n = =1) {puts ("1"); Continue; } s=1;  for(t =2; t <= N; t++) {//Enumerate an end pointinit ();  for(inti =1; I <= m; i++) {Add (Inp[i].y+ n,inp[i].x, INF);//Split EdgeAdd (Inp[i].x,inp[i].y + N,0); Add (inp[i].x+n,inp[i].y, INF); Add (inp[i].y,inp[i].x+ N,0); }            intx, y;  for(inti =1; I <= N; i++)              if(I! = s && i! =t) Add (i,i+n,1), add (I+n,i,0);//set the Benquan between the split points to 1            intTMP =0, Maxflow =0; S+=N;  while(BFS ())//maximum flow minimum cut               while(TMP = Dinic (s,inf)) Maxflow + =tmp; Ans=min (ans,maxflow); S-=N; }        if(ans = = INF) printf ("%d\n", N); Elseprintf"%d\n", ans); }    return 0;}

POJ 1966 Cable TV Network