Merge pull request #678 from Ride010/main

Detect Loop in linked list.cpp

Author: Sirajmolla

Linked List Basics/Detect Loop in linked list.cpp

@@ -0,0 +1,87 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+struct Node
+{
+    int data;
+    Node* next;
+    
+    Node(int val)
+    {
+        data = val;
+        next = NULL;
+    }
+};
+
+void loopHere(Node* head, Node* tail, int position)
+{
+    if(position==0) return;
+    
+    Node* walk = head;
+    for(int i=1; i<position; i++)
+        walk = walk->next;
+    tail->next = walk;
+}
+
+bool detectLoop(Node* head);
+
+int main()
+{
+    int t;
+    cin>>t;
+    while(t--)
+    {
+        int n, num;
+        cin>>n;
+        
+        Node *head, *tail;
+        cin>> num;
+        head = tail = new Node(num);
+        
+        for(int i=0 ; i<n-1 ; i++)
+        {
+            cin>> num;
+            tail->next = new Node(num);
+            tail = tail->next;
+        }
+        
+        int pos;
+        cin>> pos;
+        loopHere(head,tail,pos);
+        
+        if( detectLoop(head) )
+            cout<< "True\n";
+        else
+            cout<< "False\n";
+    }
+	return 0;
+}
+// } Driver Code Ends
+
+
+/*
+
+struct Node
+{
+    int data;
+    struct Node *next;
+    Node(int x) {
+        data = x;
+        next = NULL;
+    }
+
+*/
+
+bool detectLoop(Node* head)
+{
+    // your code here
+    Node *slow=head,*fast=head;
+    while(fast!=NULL && fast->next!=NULL)
+    {
+        slow=slow->next;
+        fast=fast->next->next;
+        if(slow==fast)
+            return 1;
+    }
+    return 0;
+}