POJ-3281 Dining (isap ek Dinic)

POJ-3281 Dining (isap ek Dinic)

There are nheaded cattle, F kinds of food, D kinds of drinks, each type of food and drink only one
Now, I will show you the foods and drinks that each ox loves. I will ask you how many cows can get their favorite foods and drinks at most.

Solution: Split the ox into two points. The weight is 1. One item is connected to the favorite food, the weight is 1, and the other is connected to the favorite drink. The weight is 1.
Connect all the food to the super source. The weight is 1.
Connect all drinks to super destinations with a weight of 1

ISAP

#include 
  
   #include 
   
    #include #include 
    
     #include 
     
      using namespace std;#define N 1010#define INF 0x3f3f3f3fstruct Edge {    int from, to, cap, flow;    Edge() {}    Edge(int from, int to, int cap, int flow): from(from), to(to), cap(cap), flow(flow) {}};struct ISAP {    int p[N], num[N], cur[N], d[N];    int t, s, n, m;    bool vis[N];    vector
      
        G[N]; vector
       
         edges; void init(int n) { this->n = n; for (int i = 0; i <= n; i++) { G[i].clear(); d[i] = INF; } edges.clear(); } void AddEdge(int from, int to, int cap) { edges.push_back(Edge(from, to, cap, 0)); edges.push_back(Edge(to, from, 0, 0)); int m = edges.size(); G[from].push_back(m - 2); G[to].push_back(m - 1); } bool BFS() { memset(vis, 0, sizeof(vis)); queue
        
          Q; d[t] = 0; vis[t] = 1; Q.push(t); while (!Q.empty()) { int u = Q.front(); Q.pop(); for (int i = 0; i < G[u].size(); i++) { Edge &e = edges[G[u][i] ^ 1]; if (!vis[e.from] && e.cap > e.flow) { vis[e.from] = true; d[e.from] = d[u] + 1; Q.push(e.from); } } } return vis[s]; } int Augment() { int u = t, flow = INF; while (u != s) { Edge &e = edges[p[u]]; flow = min(flow, e.cap - e.flow); u = edges[p[u]].from; } u = t; while (u != s) { edges[p[u]].flow += flow; edges[p[u] ^ 1].flow -= flow; u = edges[p[u]].from; } return flow; } int Maxflow(int s, int t) { this->s = s; this->t = t; int flow = 0; BFS(); if (d[s] > n) return 0; memset(num, 0, sizeof(num)); memset(cur, 0, sizeof(cur)); for (int i = 0; i < n; i++) if (d[i] < INF) num[d[i]]++; int u = s; while (d[s] <= n) { if (u == t) { flow += Augment(); u = s; } bool ok = false; for (int i = cur[u]; i < G[u].size(); i++) { Edge &e = edges[G[u][i]]; if (e.cap > e.flow && d[u] == d[e.to] + 1) { ok = true; p[e.to] = G[u][i]; cur[u] = i; u = e.to; break; } } if (!ok) { int Min = n; for (int i = 0; i < G[u].size(); i++) { Edge &e = edges[G[u][i]]; if (e.cap > e.flow) Min = min(Min, d[e.to]); } if (--num[d[u]] == 0) break; num[d[u] = Min + 1]++; cur[u] = 0; if (u != s) u = edges[p[u]].from; } } return flow; }};//cow 1 -- 2 * n//food 2 * n + 1 --- 2 * n + f//drink 2 * n + f + 1 --- 2 * n + f + d//start 0//sink 2 * n + f + d + 1ISAP isap;int n, f, d;void init() { int s = 0, t = 2 * n + d + f + 1; isap.init(t); for (int i = 1; i <= f; i++) { isap.AddEdge(0, 2 * n + i, 1); } for (int i = 1; i <= d; i++) { isap.AddEdge(2 * n + f + i, t, 1); } int fi, di, x; for (int i = 1; i <= n; i++) { scanf(%d%d, &fi, &di); isap.AddEdge(i, n + i, 1); for (int j = 0; j < fi; j++) { scanf(%d, &x); isap.AddEdge(2 * n + x, i, 1); } for (int j = 0; j < di; j++) { scanf(%d, &x); isap.AddEdge(n + i, 2 * n + f + x, 1); } } int flow = isap.Maxflow(s, t); printf(%d, flow);}int main() { while (scanf(%d%d%d, &n, &f, &d) != EOF) { init(); } return 0;}
        
       
      
     
    
   
  

Dinic

#include 
  
   #include 
   
    #include #include 
    
     #include 
     
      using namespace std;#define N 1010#define INF 0x3f3f3f3fstruct Edge{    int from, to, cap, flow;    Edge() {}    Edge(int from, int to, int cap, int flow) : from(from), to(to), cap(cap), flow(flow) {}};struct Dinic{    int n, m, s, t;    vector
      
        edges; vector
       
         G[N]; bool vis[N]; int d[N], cur[N]; void init(int n) { this->n = n; for (int i = 0; i <= n; i++) { G[i].clear(); } edges.clear(); } void AddEdge(int from, int to, int cap) { edges.push_back(Edge(from, to, cap, 0)); edges.push_back(Edge(to, from, 0, 0)); int m = edges.size(); G[from].push_back(m - 2); G[to].push_back(m - 1); } bool BFS() { memset(vis, 0, sizeof(vis)); queue
        
          Q; Q.push(s); vis[s] = 1; d[s] = 0; while (!Q.empty()) { int u = Q.front(); Q.pop(); for (int i = 0; i < G[u].size(); i++) { Edge &e = edges[G[u][i]]; if (!vis[e.to] && e.cap > e.flow) { vis[e.to] = true; d[e.to] = d[u] + 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; }};Dinic dinic;//cow 1 -- 2 * n//food 2 * n + 1 --- 2 * n + f//drink 2 * n + f + 1 --- 2 * n + f + d//start 0//sink 2 * n + f + d + 1int n, f, d;void init() { int s = 0, t = 2 * n + d + f + 1; dinic.init(t); for (int i = 1; i <= f; i++) { dinic.AddEdge(0, 2 * n + i, 1); } for (int i = 1; i <= d; i++) { dinic.AddEdge(2 * n + f + i, t, 1); } int fi, di, x; for (int i = 1; i <= n; i++) { scanf(%d%d, &fi, &di); dinic.AddEdge(i, n + i, 1); for (int j = 0; j < fi; j++) { scanf(%d, &x); dinic.AddEdge(2 * n + x, i, 1); } for (int j = 0; j < di; j++) { scanf(%d, &x); dinic.AddEdge(n + i, 2 * n + f + x, 1); } } int flow = dinic.Maxflow(s, t); printf(%d, flow);}int main() { while (scanf(%d%d%d, &n, &f, &d) != EOF) { init(); } return 0;}
        
       
      
     
    
   
  

EK

#include 
  
   #include 
   
    #include 
    
     #include #include 
     
      using namespace std;#define N 1010#define INF 0x3f3f3f3fstruct Edge{    int from, to, cap, flow;    Edge() {}    Edge(int from, int to, int cap, int flow): from(from), to(to), cap(cap), flow(flow){}};struct EK{    vector
      
        G[N]; vector
       
         edges; int s, t, n, m, p[N]; bool vis[N]; void init(int n) { this->n = n; for (int i = 0; i <= n; i++) G[i].clear(); edges.clear(); } 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() { queue
        
          q; memset(vis, 0, sizeof(vis)); vis[s] = 1; q.push(s); while (!q.empty()) { int u = q.front(); q.pop(); for (int i = 0; i < G[u].size(); i++) { Edge &e = edges[G[u][i]]; if (!vis[e.to] && e.cap > e.flow) { vis[e.to] = true; p[e.to] = G[u][i]; if (e.to == t) return true; q.push(e.to); } } } return false; } int Augment() { int flow = INF, u = t; while (u != s) { Edge &e = edges[p[u]]; flow = min(flow, e.cap - e.flow); u = e.from; } u = t; while (u != s) { edges[p[u]].flow += flow; edges[p[u] ^ 1].flow -= flow; u = edges[p[u]].from; } return flow; } int Maxflow(int s, int t) { this->s = s; this->t = t; int flow = 0; while (BFS()) { flow += Augment(); } return flow; }};EK ek;//cow 1 -- 2 * n//food 2 * n + 1 --- 2 * n + f//drink 2 * n + f + 1 --- 2 * n + f + d//start 0//sink 2 * n + f + d + 1int n, f, d;void init() { int s = 0, t = 2 * n + d + f + 1; ek.init(t); for (int i = 1; i <= f; i++) { ek.AddEdge(0, 2 * n + i, 1); } for (int i = 1; i <= d; i++) { ek.AddEdge(2 * n + f + i, t, 1); } int fi, di, x; for (int i = 1; i <= n; i++) { scanf(%d%d, &fi, &di); ek.AddEdge(i, n + i, 1); for (int j = 0; j < fi; j++) { scanf(%d, &x); ek.AddEdge(2 * n + x, i, 1); } for (int j = 0; j < di; j++) { scanf(%d, &x); ek.AddEdge(n + i, 2 * n + f + x, 1); } } int flow = ek.Maxflow(s, t); printf(%d, flow);}int main() { while (scanf(%d%d%d, &n, &f, &d) != EOF) { init(); } return 0;}