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keep code consistent

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Evan Ferrao 2026-02-14 15:24:35 +05:30 committed by GitHub
parent 046371022d
commit c583b04984
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2 changed files with 65 additions and 68 deletions
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75
Graphs/CycleDetectionBFS.java
View File

@ -1,67 +1,68 @@
import java.util.*; import java.util.*;
import java.io.*;
public class CycleDetectionBFS { class Main {
static class Pair { // helper structure
int first; static class Node{
int second; int node;
int parent;
Pair(int first, int second) { Node(int node, int parent){
this.first = first; this.node = node;
this.second = second; this.parent = parent;
} }
} }
public static boolean bfs(int src, int V, ArrayList<ArrayList<Integer>> adj,boolean[] vis) { public static boolean bfs(int src, int V,
ArrayList<ArrayList<Integer>> adj,
boolean visited[]){
vis[src] = true; visited[src] = true;
Queue<Pair> q = new LinkedList<>();
q.add(new Pair(src, -1));
while (!q.isEmpty()) { Queue<Node> q = new LinkedList<>();
int node = q.peek().first; q.add(new Node(src, -1));
int parent = q.peek().second;
q.remove();
for (int adjacentNode : adj.get(node)) { while(!q.isEmpty()){
if (!vis[adjacentNode]) { Node cur = q.poll();
vis[adjacentNode] = true; int u = cur.node;
q.add(new Pair(adjacentNode, node)); int par = cur.parent;
for(int v : adj.get(u)){
if(!visited[v]){
visited[v] = true;
q.add(new Node(v, u));
} }
else if(v != par){
// everything except this 'else if' statement is normal BFS return true; // cycle
else if (adjacentNode != parent) {
return true; // cycle detected
} }
} }
} }
return false; return false;
} }
public static boolean isCycle(int V, ArrayList<ArrayList<Integer>> adj) { public static boolean isCycle(int V, ArrayList<ArrayList<Integer>> adj){
boolean[] vis = new boolean[V]; boolean visited[] = new boolean[V];
for (int i = 0; i < V; i++) { for(int i=0;i<V;i++){
if (!vis[i]) { if(!visited[i]){
if (bfs(i, V, adj, vis)) { if(bfs(i, V, adj, visited)) return true;
return true;
}
} }
} }
return false; return false;
} }
public static void main(String[] args) {
// ================= DRIVER =================
public static void main(String args[]){
int V = 5; int V = 5;
ArrayList<ArrayList<Integer>> adj = new ArrayList<>(); ArrayList<ArrayList<Integer>> adj = new ArrayList<>();
for (int i = 0; i < V; i++) { for(int i=0;i<V;i++) adj.add(new ArrayList<>());
adj.add(new ArrayList<>());
}
// Undirected graph edges // Undirected graph
adj.get(0).add(1); adj.get(0).add(1);
adj.get(1).add(0); adj.get(1).add(0);
@ -71,12 +72,12 @@ public class CycleDetectionBFS {
adj.get(2).add(3); adj.get(2).add(3);
adj.get(3).add(2); adj.get(3).add(2);
adj.get(3).add(1); // creates a cycle adj.get(3).add(1);
adj.get(1).add(3); adj.get(1).add(3);
adj.get(3).add(4); adj.get(3).add(4);
adj.get(4).add(3); adj.get(4).add(3);
System.out.printf(isCycle(V, adj) ? "Cycle detected" : "No cycle detected"); System.out.printf(isCycle(V, adj) ? "Cycle detected\n" : "No cycle detected\n");
} }
} }

58
Graphs/CycleDetectionDFS.java
View File

@ -1,64 +1,60 @@
import java.util.*; import java.util.*;
import java.io.*;
public class CycleDetectionDFS { class Main {
static class Pair { // helper structure
static class Node{
int node; int node;
int parent; int parent;
Pair(int node, int parent) { Node(int node, int parent){
this.node = node; this.node = node;
this.parent = parent; this.parent = parent;
} }
} }
public static boolean dfs(Pair current, boolean[] vis, ArrayList<ArrayList<Integer>> adj) { public static boolean dfs(Node cur, boolean visited[],
ArrayList<ArrayList<Integer>> adj){
int node = current.node; int u = cur.node;
int parent = current.parent; int par = cur.parent;
vis[node] = true; visited[u] = true;
for (int adjacentNode : adj.get(node)) { for(int v : adj.get(u)){
if(!visited[v]){
if (!vis[adjacentNode]) { if(dfs(new Node(v, u), visited, adj)) return true;
if (dfs(new Pair(adjacentNode, node), vis, adj)) {
return true;
}
} }
else if(v != par){
// everything except this 'else if' statement is normal DFS return true; // cycle
else if (adjacentNode != parent) {
return true;
} }
} }
return false; return false;
} }
public static boolean isCycle(int V, ArrayList<ArrayList<Integer>> adj) { public static boolean isCycle(int V, ArrayList<ArrayList<Integer>> adj){
boolean[] vis = new boolean[V]; boolean visited[] = new boolean[V];
for (int i = 0; i < V; i++) { for(int i=0;i<V;i++){
if (!vis[i]) { if(!visited[i]){
if (dfs(new Pair(i, -1), vis, adj)) { if(dfs(new Node(i, -1), visited, adj)) return true;
return true;
}
} }
} }
return false; return false;
} }
public static void main(String[] args) {
// ================= DRIVER =================
public static void main(String args[]){
int V = 5; int V = 5;
ArrayList<ArrayList<Integer>> adj = new ArrayList<>(); ArrayList<ArrayList<Integer>> adj = new ArrayList<>();
for (int i = 0; i < V; i++) { for(int i=0;i<V;i++) adj.add(new ArrayList<>());
adj.add(new ArrayList<>());
}
// Undirected graph edges // Undirected graph
adj.get(0).add(1); adj.get(0).add(1);
adj.get(1).add(0); adj.get(1).add(0);
@ -68,12 +64,12 @@ public class CycleDetectionDFS {
adj.get(2).add(3); adj.get(2).add(3);
adj.get(3).add(2); adj.get(3).add(2);
adj.get(3).add(1); // creates a cycle adj.get(3).add(1);
adj.get(1).add(3); adj.get(1).add(3);
adj.get(3).add(4); adj.get(3).add(4);
adj.get(4).add(3); adj.get(4).add(3);
System.out.printf(isCycle(V, adj) ? "Cycle detected" : "No cycle detected"); System.out.printf(isCycle(V, adj) ? "Cycle detected\n" : "No cycle detected\n");
} }
} }