chore(CPlusPlus): add segregate-even-odd-nodes-of-linked list (#452)

algorithms/CPlusPlus/Linked-Lists/segregate-even-odd-nodes-of-linked-list.cpp

@@ -0,0 +1,99 @@
+/*
+The idea is to split the linked list into two: 
+one containing all even nodes and other containing all odd nodes. 
+And finally, attach the odd node linked list after the even node linked list. 
+To split the Linked List, traverse the original Linked List and move all odd nodes to a separate Linked List of all odd nodes. 
+At the end of loop, the original list will have all the even nodes and the odd node list will have all the odd nodes. 
+To keep the ordering of all nodes same, we must insert all the odd nodes at the end of the even node list. 
+And to do that in constant time, we must keep track of last pointer in the even node list
+*/
+
+#include <bits/stdc++.h> 
+using namespace std; 
+
+/* a node of the singly linked list */
+struct Node{
+    int data;
+    Node* next;
+    Node(int x){
+        data=x;
+        next=NULL;
+    }
+};
+
+/* Function to print nodes in a given linked list */
+void printlist(Node *head){
+    Node *curr=head;
+    while(curr!=NULL){
+        cout<<curr->data<<" ";
+        curr=curr->next;
+    }cout<<endl;
+}
+// Function to segregate even and odd nodes.
+Node *segregate(Node *head){
+	// Starting node of list having
+    // even values.
+    Node *eS=NULL;
+    // Ending node of even values list.
+	Node *eE=NULL;
+	// Starting node of odd values list.
+	Node *oS=NULL;
+	// Ending node of odd values list.
+	Node *oE=NULL;
+    for(Node *curr=head;curr!=NULL;curr=curr->next){
+        int x=curr->data;
+        // If current value is even, add
+        // it to even values list.
+        if(x%2==0){
+            if(eS==NULL){
+                eS=curr;
+                eE=eS;
+            }else{
+                eE->next=curr;
+                eE=eE->next;
+            }
+        }
+		// If current value is odd, add
+        // it to odd values list.
+		else{
+            if(oS==NULL){
+                oS=curr;
+                oE=oS;
+            }else{
+                oE->next=curr;
+                oE=oE->next;
+            }
+        }
+    }
+    // If either odd list or even list is empty,
+    // no change is required as all elements
+    // are either even or odd.
+    if(oS==NULL||eS==NULL)
+        return head;
+    // Add odd list after even list.     
+    eE->next=oS;
+    oE->next=NULL;
+    return eS;
+}
+
+/* Driver program to test above functions*/
+int main() 
+{ 
+	Node *head=new Node(10);
+	head->next=new Node(11);
+	head->next->next=new Node(12);
+	head->next->next->next=new Node(13);
+	head->next->next->next->next=new Node(14);
+	head->next->next->next->next->next=new Node(15);
+	printlist(head);
+	head=segregate(head);
+	printlist(head);
+	return 0;
+}
+
+/*
+Input: 10 11 12 13 14 15
+Output: 10 12 14 11 13 15
+
+Time complexity: O(n)
+*/ 

algorithms/CPlusPlus/README.md

@@ -45,6 +45,7 @@
 8. [Reorder List](Linked-Lists/Reorder-List.cpp)
 9. [Detecting cycle in a singly linked list](Linked-Lists/Cycle-Detection.cpp)
 10. [Find Merge Point of two singly linked list](Linked-Lists/Find-Merge-Point.cpp)
+11. [Segregate Even Odd Nodes of linked list](Linked-Lists/segregate-even-odd-nodes-of-linked-list.cpp)
 
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