Sha 1345-Jamie's contact groups (two points + maximum Stream)

Sha 1345-Jamie's contact groups

Question Link

Question: given some people, each person has a group. Now everyone needs to select a group to minimize the maximum number of people in all groups.

Train of Thought: The second answer, and then use the maximum flow to determine, the source point to each person to build an edge capacity of 1, each person to their own group to build an edge capacity of 1, the Group creates an edge for the vertex, And the capacity is a binary value. In this way, the maximum stream is run. If the maximum stream is equal to N, it can meet the requirements.

Code:

#include <cstdio>#include <cstring>#include <queue>#include <algorithm>#include <map>#include <string>#include <iostream>#include <set>using namespace std;const int MAXNODE = 1505;const int MAXEDGE = 1100005;typedef int Type;const Type INF = 0x3f3f3f3f;struct Edge {int u, v;Type cap, flow;Edge() {}Edge(int u, int v, Type cap, Type 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];Type d[MAXNODE];int cur[MAXNODE];vector<int> cut;void init(int n) {this->n = n;memset(first, -1, sizeof(first));m = 0;}void add_Edge(int u, int v, Type 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];}Type dfs(int u, Type a) {if (u == t || a == 0) return a;Type 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;}bool Maxflow(int s, int t, int tot) {this->s = s; this->t = t;Type flow = 0;while (bfs()) {for (int i = 0; i < n; i++)cur[i] = first[i];flow += dfs(s, INF);}return flow == tot;}void MinCut() {cut.clear();for (int i = 0; i < m; i += 2) {if (vis[edges[i].u] && !vis[edges[i].v])cut.push_back(i);}}} gao;const int N = 1005;const int M = 505;int n, m, cnt[M];vector<int> f[N];char str[100005];bool judge(int c) {gao.init(n + m + 2);int s = 0, t = n + m + 1;for (int i = 0; i < n; i++) {gao.add_Edge(0, i + 1, 1);for (int j = 0; j < f[i].size(); j++) {gao.add_Edge(i + 1, f[i][j] + n + 1, 1);}}for (int i = 0; i < m; i++)gao.add_Edge(n + i + 1, t, c);return gao.Maxflow(s, t, n);}int main() {while (~scanf("%d%d", &n, &m) && n || m) {memset(cnt, 0, sizeof(cnt));while ((getchar()) != '\n');for (int i = 0; i < n; i++) {f[i].clear();gets(str);int len = strlen(str);int sum = 0;int flag = 0;for (int j = 0; j < len; j++) {if (str[j] >= '0' && str[j] <= '9') {flag = 1;sum = sum * 10 + str[j] - '0';} else {if (flag) {f[i].push_back(sum);cnt[sum]++;}flag = 0;sum = 0;}}if (flag) {f[i].push_back(sum);cnt[sum]++;}}int l = 0, r = 0;for (int i = 0; i < m; i++) r = max(r, cnt[i]);while (l < r) {int mid = (l + r) / 2;if (judge(mid)) r = mid;else l = mid + 1;}printf("%d\n", l);}return 0;}

Sha 1345-Jamie's contact groups (two points + maximum Stream)