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MinCostFlow.java
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208 lines (191 loc) · 6.33 KB
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/**
* @verified
* - https://atcoder.jp/contests/practice2/tasks/practice2_e
* - http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=GRL_6_B
*/
class MinCostFlow {
public class WeightedCapEdge {
private final int from, to;
private long cap;
private long cost;
private final int rev;
WeightedCapEdge(int from, int to, long cap, long cost, int rev) {
this.from = from;
this.to = to;
this.cap = cap;
this.cost = cost;
this.rev = rev;
}
public int getFrom() {return from;}
public int getTo() {return to;}
public long getCap() {return cap;}
public long getCost() {return cost;}
public long getFlow() {return g[to][rev].cap;}
}
private static final long INF = Long.MAX_VALUE;
private final int n;
private int m;
private final java.util.ArrayList<WeightedCapEdge> edges;
private final int[] count;
private final WeightedCapEdge[][] g;
private final long[] potential;
private final long[] dist;
private final WeightedCapEdge[] prev;
public MinCostFlow(int n) {
this.n = n;
this.edges = new java.util.ArrayList<>();
this.count = new int[n];
this.g = new WeightedCapEdge[n][];
this.potential = new long[n];
this.dist = new long[n];
this.prev = new WeightedCapEdge[n];
}
public int addEdge(int from, int to, long cap, long cost) {
rangeCheck(from, 0, n);
rangeCheck(to, 0, n);
nonNegativeCheck(cap, "Capacity");
nonNegativeCheck(cost, "Cost");
WeightedCapEdge e = new WeightedCapEdge(from, to, cap, cost, count[to]);
count[from]++; count[to]++;
edges.add(e);
return m++;
}
private void buildGraph() {
for (int i = 0; i < n; i++) {
g[i] = new WeightedCapEdge[count[i]];
}
int[] idx = new int[n];
for (WeightedCapEdge e : edges) {
g[e.to][idx[e.to]++] = new WeightedCapEdge(e.to, e.from, 0, -e.cost, idx[e.from]);
g[e.from][idx[e.from]++] = e;
}
}
private long addFlow;
private long addCost;
public long[] minCostMaxFlow(int s, int t) {
return minCostFlow(s, t, INF);
}
public long[] minCostFlow(int s, int t, long flowLimit) {
rangeCheck(s, 0, n);
rangeCheck(t, 0, n);
if (s == t) {
throw new IllegalArgumentException(String.format("s = t = %d", s));
}
nonNegativeCheck(flowLimit, "Flow");
buildGraph();
long flow = 0;
long cost = 0;
while (true) {
dijkstra(s, t, flowLimit - flow);
if (addFlow == 0) break;
flow += addFlow;
cost += addFlow * addCost;
}
return new long[]{flow, cost};
}
public java.util.ArrayList<long[]> minCostSlope(int s, int t) {
return minCostSlope(s, t, INF);
}
public java.util.ArrayList<long[]> minCostSlope(int s, int t, long flowLimit) {
rangeCheck(s, 0, n);
rangeCheck(t, 0, n);
if (s == t) {
throw new IllegalArgumentException(String.format("s = t = %d", s));
}
nonNegativeCheck(flowLimit, "Flow");
buildGraph();
java.util.ArrayList<long[]> slope = new java.util.ArrayList<>();
long prevCost = -1;
long flow = 0;
long cost = 0;
while (true) {
slope.add(new long[]{flow, cost});
dijkstra(s, t, flowLimit - flow);
if (addFlow == 0) return slope;
flow += addFlow;
cost += addFlow * addCost;
if (addCost == prevCost) {
slope.remove(slope.size() - 1);
}
prevCost = addCost;
}
}
private void dijkstra(int s, int t, long maxFlow) {
final class State implements Comparable<State> {
final int v;
final long d;
State(int v, long d) {this.v = v; this.d = d;}
public int compareTo(State s) {return d == s.d ? v - s.v : d > s.d ? 1 : -1;}
}
java.util.Arrays.fill(dist, INF);
dist[s] = 0;
java.util.PriorityQueue<State> pq = new java.util.PriorityQueue<>();
pq.add(new State(s, 0l));
while (pq.size() > 0) {
State st = pq.poll();
int u = st.v;
if (st.d != dist[u]) continue;
for (WeightedCapEdge e : g[u]) {
if (e.cap <= 0) continue;
int v = e.to;
long nextCost = dist[u] + e.cost + potential[u] - potential[v];
if (nextCost < dist[v]) {
dist[v] = nextCost;
prev[v] = e;
pq.add(new State(v, dist[v]));
}
}
}
if (dist[t] == INF) {
addFlow = 0;
addCost = INF;
return;
}
for (int i = 0; i < n; i++) {
potential[i] += dist[i];
}
addCost = 0;
addFlow = maxFlow;
for (int v = t; v != s;) {
WeightedCapEdge e = prev[v];
addCost += e.cost;
addFlow = java.lang.Math.min(addFlow, e.cap);
v = e.from;
}
for (int v = t; v != s;) {
WeightedCapEdge e = prev[v];
e.cap -= addFlow;
g[v][e.rev].cap += addFlow;
v = e.from;
}
}
public void clearFlow() {
java.util.Arrays.fill(potential, 0);
for (WeightedCapEdge e : edges) {
long flow = e.getFlow();
e.cap += flow;
g[e.to][e.rev].cap -= flow;
}
}
public WeightedCapEdge getEdge(int i) {
rangeCheck(i, 0, m);
return edges.get(i);
}
public java.util.ArrayList<WeightedCapEdge> getEdges() {
return edges;
}
private void rangeCheck(int i, int minInlusive, int maxExclusive) {
if (i < 0 || i >= maxExclusive) {
throw new IndexOutOfBoundsException(
String.format("Index %d out of bounds for length %d", i, maxExclusive)
);
}
}
private void nonNegativeCheck(long cap, java.lang.String attribute) {
if (cap < 0) {
throw new IllegalArgumentException(
String.format("%s %d is negative.", attribute, cap)
);
}
}
}