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detect-cycle-using-dsu.java
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detect-cycle-using-dsu.java
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class Solution{
private int[] parent;
private int[] depth;
public int findparent(int vertex){
if(vertex == parent[vertex]){
return vertex;
}
return parent[vertex] = findparent(parent[vertex]);
}
public int detectCycle(int n, ArrayList<ArrayList<Integer>> adj){
parent = new int[n];
depth = new int[n];
Map<Integer, Map<Integer, Integer>> mp = new HashMap<>();
Arrays.fill(depth, 1);
for(int i = 0; i < n; i++){
parent[i] = i;
}
for(int a = 0; a < n; a++){
for(int b : adj.get(a)){
if(mp.containsKey(a) && mp.get(a).containsKey(b)){
continue;
}
if(mp.containsKey(b) && mp.get(b).containsKey(a)){
continue;
}
if(!mp.containsKey(a)){
mp.put(a, new HashMap<>());
}
mp.get(a).put(b, 1);
int a_parent = findparent(a);
int b_parent = findparent(b);
if(a_parent != b_parent){
if(depth[a_parent] > depth[b_parent]){
parent[b_parent] = a_parent;
depth[a_parent] += depth[b_parent];
}else if(depth[a_parent] < depth[b_parent]){
parent[a_parent] = b_parent;
depth[b_parent] += depth[a_parent];
}else{
parent[a_parent] = b_parent;
depth[b_parent] += depth[a_parent];
}
}else{
return 1;
}
}
}
return 0;
}
}