POJ: Dining

4 3 3
2 2 1 2 3 1
2 2 2 3 1 2
2 2 1 3 1 2
2 1 1 3 3
3
#include <cstdio>
#include <vector>
#include <queue>
using namespace std;#define MAX_N 100
#define MAX_F 100
#define MAX_D 100
#define MAX_V ((MAX_N) * 2 + (MAX_D) + (MAX_F) + 2)
#define INF 0x3f3f3f3f
struct SEdge {
int to;
int cap;
int rev;
SEdge(int t, int c, int r): to(t), cap(c), rev(r) {}
};
vector<SEdge> G[MAX_V];
int level[MAX_V];
int iter[MAX_V];
void add_edge(int from, int to, int cap) {
SEdge fromEdge(to, cap, (int)G[to].size());
G[from].push_back(fromEdge);
SEdge toEdge(from, 0, (int)G[from].size() - 1);
G[to].push_back(toEdge);
}
void bfs(int s) {
memset(level, -1, sizeof(level));
queue<int> q;
level[s] = 0;
q.push(s);
while (!q.empty()) {
int v = q.front();
q.pop();
for (int i = 0; i < G[v].size(); ++i) {
SEdge &e = G[v][i];
if (e.cap > 0 && level[e.to] < 0) {
level[e.to] = level[v] + 1;
q.push(e.to);
}
}
}
}
int dfs(int v, int t, int f) {
if (v == t) return f;
for (int &i = iter[v]; i < G[v].size(); ++i) {
SEdge &e = G[v][i];
if (e.cap > 0 && level[v] < level[e.to]) {
int d = dfs(e.to, t, min(f, e.cap));
if (d > 0) {
e.cap -= d;
G[e.to][e.rev].cap += d;
return d;
}
}
}
return 0;
}
int max_flow(int s, int t) {
int flow = 0;
while (true) {
bfs(s);
if (level[t] < 0) return flow;
memset(iter, 0, sizeof(iter));
int f;
while ((f = dfs(s, t, INF)) > 0) flow += f;
}
}
int main(int argc, char *argv[]) {
int N,F,D;
bool likeF[MAX_N][MAX_F];
bool likeD[MAX_N][MAX_D];
memset(likeF, '\0', sizeof(likeF));
memset(likeD, '\0', sizeof(likeD));
scanf("%d%d%d", &N, &F, &D); for (int i = 0; i < N; ++i) {
getchar();
int countF, countD;
scanf("%d%d", &countF, &countD);
for (int j = 0; j < countF; ++j) {
int k;
scanf("%d", &k);
likeF[i][k - 1] = true;
}
for (int j = 0; j < countD; ++j) {
int k;
scanf("%d", &k);
likeD[i][k - 1] = true;
}
}
// N~2N-1: cow in drink part
// 2N~2N+F-1: food
// 2N+F~2N+F+D-1: drink
int s = N * 2 + F + D;
int t = s + 1;
for (int i = 0; i < F; ++i)
add_edge(s, N * 2 + i, 1);
for (int i = 0; i < D; ++i)
add_edge(N * 2 + F + i, t, 1);

for (int i = 0; i < N; ++i) {
add_edge(i, N + i, 1);
for (int j = 0; j < F; ++j) {
if (likeF[i][j]) add_edge(N * 2 + j, i, 1);
}
for (int j = 0; j < D; ++j) {
if (likeD[i][j]) add_edge(N + i, N * 2 + F + j, 1);
}
}
printf("%d\n", max_flow(s, t));

return 0;
}

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