[蓝书/Ch5] Collectors Problem UVA

题目链接

把物品作为点,物品的交换通过与物品点的连线实现

#include<bits/stdc++.h>using namespace std;typedef long long ll;const int maxn = 1000 + 10;const int INF = 1000000000;struct Edge {  int from, to, cap, flow;};bool operator < (const Edge& a, const Edge& b) {  return a.from < b.from || (a.from == b.from && a.to < b.to);}struct Dinic {  int n, m, s, t;  vector<Edge> edges;    // 边数的两倍  vector<int> G[maxn];   // 邻接表，G[i][j]表示结点i的第j条边在e数组中的序号  bool vis[maxn];         // BFS使用  int d[maxn];           // 从起点到i的距离  int cur[maxn];        // 当前弧指针  void ClearAll(int n) {    for(int i = 0; i < n; i++) G[i].clear();    edges.clear();  }  void ClearFlow() {    for(int i = 0; i < edges.size(); i++) edges[i].flow = 0;  }  void AddEdge(int from, int to, int cap) {    edges.push_back((Edge){from, to, cap, 0});    edges.push_back((Edge){to, from, 0, 0});    m = edges.size();    G[from].push_back(m-2);    G[to].push_back(m-1);  }  bool BFS() {    memset(vis, 0, sizeof(vis));    queue<int> Q;    Q.push(s);    vis[s] = 1;    d[s] = 0;    while(!Q.empty()) {      int x = Q.front(); Q.pop();      for(int i = 0; i < G[x].size(); i++) {        Edge& e = edges[G[x][i]];        if(!vis[e.to] && e.cap > e.flow) {          vis[e.to] = 1;          d[e.to] = d[x] + 1;          Q.push(e.to);        }      }    }    return vis[t];  }  int DFS(int x, int a) {    if(x == t || a == 0) return a;    int flow = 0, f;    for(int& i = cur[x]; i < G[x].size(); i++) {      Edge& e = edges[G[x][i]];      if(d[x] + 1 == d[e.to] && (f = DFS(e.to, min(a, e.cap-e.flow))) > 0) {        e.flow += f;        edges[G[x][i]^1].flow -= f;        flow += f;        a -= f;        if(a == 0) break;      }    }    return flow;  }  int Maxflow(int s, int t) {    this->s = s; this->t = t;    int flow = 0;    while(BFS()) {      memset(cur, 0, sizeof(cur));      flow += DFS(s, INF);    }    return flow;  }  vector<int> Mincut() { // call this after maxflow    vector<int> ans;    for(int i = 0; i < edges.size(); i++) {      Edge& e = edges[i];      if(vis[e.from] && !vis[e.to] && e.cap > 0) ans.push_back(i);    }    return ans;  }  void Reduce() {    for(int i = 0; i < edges.size(); i++) edges[i].cap -= edges[i].flow;  }};Dinic g;int n,m,k;int T;int a[15][50];int cas;int main(){//    freopen("data.txt","r",stdin);    ios_base::sync_with_stdio(false);    cin >> T;    cas=0;    while(T--)    {        cas++;        memset(a,0,sizeof(a));        cin >> n>>m;        for(int i=1;i<=n;i++)        {            cin >> k;            int tp;            for(int j=1;j<=k;j++)            {                cin >> tp;                a[i][tp]++;            }        }        int s = m+1;        int t = m+n+1;        g.ClearAll(t+5);        for(int j=1;j<=m;j++)        {            if(a[1][j])            g.AddEdge(s,j,a[1][j]);        }        for(int i=2;i<=n;i++)        {            int now = i+m;            for(int j=1;j<=m;j++)            {                if(a[i][j]>1)                {                    g.AddEdge(now,j,a[i][j]-1);                }                if(a[i][j]==0)                {                    g.AddEdge(j,now,1);                }            }        }        for(int i=1;i<=m;i++)        {            g.AddEdge(i,t,1);        }        cout << "Case #"<<cas<<": "<<g.Maxflow(s,t)<<endl;    }    return 0;}