61 lines
1.4 KiB
Java
61 lines
1.4 KiB
Java
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import java.util.*;
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import java.util.stream.Stream;
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public class MaxFlowEdmondsKarp {
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static class Edge {
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int s, t, rev, cap, f;
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public Edge(int s, int t, int rev, int cap) {
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this.s = s;
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this.t = t;
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this.rev = rev;
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this.cap = cap;
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}
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}
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public static void addEdge(List<Edge>[] graph, int s, int t, int cap) {
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graph[s].add(new Edge(s, t, graph[t].size(), cap));
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graph[t].add(new Edge(t, s, graph[s].size() - 1, 0));
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}
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public static int maxFlow(List<Edge>[] graph, int s, int t) {
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int flow = 0;
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int[] q = new int[graph.length];
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while (true) {
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int qt = 0;
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q[qt++] = s;
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Edge[] pred = new Edge[graph.length];
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for (int qh = 0; qh < qt && pred[t] == null; qh++) {
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int cur = q[qh];
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for (Edge e : graph[cur]) {
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if (pred[e.t] == null && e.cap > e.f) {
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pred[e.t] = e;
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q[qt++] = e.t;
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}
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}
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}
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if (pred[t] == null)
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break;
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int df = Integer.MAX_VALUE;
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for (int u = t; u != s; u = pred[u].s)
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df = Math.min(df, pred[u].cap - pred[u].f);
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for (int u = t; u != s; u = pred[u].s) {
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pred[u].f += df;
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graph[pred[u].t].get(pred[u].rev).f -= df;
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}
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flow += df;
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}
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return flow;
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}
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// Usage example
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public static void main(String[] args) {
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List<Edge>[] graph = Stream.generate(ArrayList::new).limit(3).toArray(List[]::new);
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addEdge(graph, 0, 1, 3);
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addEdge(graph, 0, 2, 2);
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addEdge(graph, 1, 2, 2);
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System.out.println(4 == maxFlow(graph, 0, 2));
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}
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}
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