https://stackoverflow.com/questions/3911626/find-cycle-of-shortest-length-in-a-directed-graph-with-positive-weights
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51 | package ShortestCycle;
import java.util.*;
public class Main {
public static void main(String[] args) {
System.out.println("Shortest Cycle");
Map<Integer, List<Integer>> map = new HashMap<>();
map.put(0, new ArrayList<>());
map.put(1, new ArrayList<>());
map.put(2, new ArrayList<>());
map.put(3, new ArrayList<>());
map.put(4, new ArrayList<>());
map.get(0).add(1);
map.get(0).add(2);
map.get(1).add(3);
map.get(2).add(4);
map.get(3).add(0);
map.get(4).add(3);
List<Integer> prev = new ArrayList<>();
prev.add(3);
int[] dist = new int[5];
Arrays.fill(dist, Integer.MAX_VALUE);
//dist, index
PriorityQueue<int[]> pq = new PriorityQueue<>((a,b) -> a[0]-b[0]);
pq.add(new int[]{0, 0});
while(!pq.isEmpty()){
int[] top = pq.poll();
int d = top[0], index = top[1];
if(d<dist[index]){
dist[index] = d;
if(map.containsKey(index)){
for(int next : map.get(index)){
if(d+1 < dist[next]){
pq.add(new int[]{d+1, next});
}
}
}
}
}
int min = Integer.MAX_VALUE;
for(int p : prev){
min = Math.min(min, dist[p]);
}
System.out.println(min+1);
}
}
|
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