Ultraviolet A 10779-collectors problem (Network Stream)

Va 10779-collectors Problem

Question Link

Each person has a texture. Now, 0th people need to exchange textures with others to ensure that they have as many textures as possible. Only others do not have this texture, if you have more than two other textures, you can change them.

Idea: the Key to the largest stream is how to model and link people with items on the 0th to the current capacity. If other people have items equal to 0, A person who connects an edge from the item to the person can exchange the item. If the item is greater than 1, the person who connects an edge to the item, the capacity is reduced by 1 for items (you need to keep one), connect all items to the sink point, and run the maximum stream once.

Code:

#include <cstdio>#include <cstring>#include <queue>#include <algorithm>using namespace std;const int MAXNODE = 1005;const int MAXEDGE = 100005;const int INF = 0x3f3f3f3f;struct Edge {int u, v, cap, flow;Edge() {}Edge(int u, int v, int cap, int flow) {this->u = u;this->v = v;this->cap = cap;this->flow = flow;}};struct Dinic {int n, m, s, t;Edge edges[MAXEDGE];int first[MAXNODE];int next[MAXEDGE];bool vis[MAXNODE];int d[MAXNODE];int cur[MAXNODE];void init(int n) {this->n = n;memset(first, -1, sizeof(first));m = 0;}void add_Edge(int u, int v, int cap) {edges[m] = Edge(u, v, cap, 0);next[m] = first[u];first[u] = m++;edges[m] = Edge(v, u, 0, 0);next[m] = first[v];first[v] = m++;}bool bfs() {memset(vis, false, sizeof(vis));queue<int> Q;Q.push(s);d[s] = 0;vis[s] = true;while (!Q.empty()) {int u = Q.front(); Q.pop();for (int i = first[u]; i != -1; i = next[i]) {Edge& e = edges[i];if (!vis[e.v] && e.cap > e.flow) {vis[e.v] = true;d[e.v] = d[u] + 1;Q.push(e.v);}}}return vis[t];}int dfs(int u, int a) {if (u == t || a == 0) return a;int flow = 0, f;for (int &i = cur[u]; i != -1; i = next[i]) {Edge& e = edges[i];if (d[u] + 1 == d[e.v] && (f = dfs(e.v, min(a, e.cap - e.flow))) > 0) {e.flow += f;edges[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()) {for (int i = 0; i < n; i++)cur[i] = first[i];flow += dfs(s, INF);}return flow;}} gao;const int N = 30;int T, n, m, cnt[N];int main() {int cas = 0;scanf("%d", &T);while (T--) {scanf("%d%d", &n, &m);int s = 0, t = n + m;gao.init(t + 1);for (int i = 0; i < n; i++) {int tot, tmp;memset(cnt, 0, sizeof(cnt));scanf("%d", &tot);while (tot--) {scanf("%d", &tmp);cnt[tmp]++;}if (i == 0) {for (int j = 1; j <= m; j++)if (cnt[j] > 0) gao.add_Edge(i, j + n - 1, cnt[j]);} else {for (int j = 1; j <= m; j++) {if (cnt[j] > 1) gao.add_Edge(i, j + n - 1, cnt[j] - 1);if (cnt[j] == 0) gao.add_Edge(j + n - 1, i, 1);}}}for (int i = 1; i <= m; i++)gao.add_Edge(i + n - 1, t, 1);printf("Case #%d: %d\n", ++cas, gao.Maxflow(s, t));}return 0;}

Ultraviolet A 10779-collectors problem (Network Stream)