UVA1660 Cable TV Network

#include<bits/stdc++.h>
using namespace std;

const int maxn = 102;

struct Edge
{
    int v,cap,nxt;
};

vector<Edge> E;
vector<Edge> bak;
#define PB push_back

int head[maxn];

void AddEdge(int u,int v,int c)
{
    bak.PB({v,c,head[u]});
    head[u] = bak.size()-1;
    bak.PB({u,0,head[v]});
    head[v] = bak.size()-1;
}

int S,T,cur[maxn],d[maxn],q[maxn];

bool bfs()
{
    memset(d,0,sizeof(d));
    int l = 0, r = 0;
    q[r++] = S; d[S] = 1;
    while(r>l){
        int u = q[l++];
        for(int i = head[u]; ~i; i = E[i].nxt){
            Edge &e = E[i];
            if(!d[e.v] && e.cap>0){
                d[e.v] = d[u] + 1;
                q[r++] = e.v;
            }
        }
    }
    return d[T];
}

int dfs(int u,int a)
{
    if(u == T||!a) return a;
    int flow = 0,f;
    for(int &i = cur[u]; ~i; i = E[i].nxt){
        Edge &e = E[i];
        if(d[e.v] == d[u]+1 && (f = dfs(e.v,min(a,e.cap)))>0){
            flow += f; a -= f;
            e.cap -= f; E[i^1].cap += f;
            if(!a) break;
        }
    }
    return flow;
}

const int INF = 0x3f3f3f3f;

int MaxFlow()
{
    int flow = 0;
    while(bfs()){
        memcpy(cur,head,sizeof(head));
        flow += dfs(S,INF);
    }
    return flow;
}
int n,m;

void init()
{
    memset(head,-1,sizeof(head));
    bak.clear();
}


int main()
{
    //freopen("in.txt","r",stdin);
    while(~scanf("%d%d",&n,&m)){
        init();
        for(int i = 1; i < n; i++) AddEdge(i,i+n,1);
        for(int i = 0; i < m; i++){
            int u,v; scanf(" (%d,%d)",&u,&v);
            AddEdge(u+n,v,INF); AddEdge(v+n,u,INF);
        }
        int ans = n;
        S = n;
        for(T = 1; T < n; T++){
            E = bak;
            ans = min(ans,MaxFlow());
        }
        printf("%d\n",ans);
    }
    return 0;
}