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C++ Linked List Exercises: Kth node from the Middle towards Head of a Linked List

C++ Linked List: Exercise-14 with Solution

Write a C++ program to find the kth node of a linked list by starting at the middle and moving towards the head.

Test Data:
Original list:
9 7 5 3 1
kth node of a linked list by starting at
the middle and moving towards the head:
Position = 2
Value = 9

Sample Solution:

C++ Code:

#include <iostream>

using namespace std;

struct  Node
{   
    int num;
    Node *next;
 }; //node constructed

  int size = 0;
  void insert(Node** head, int num){
    Node* new_Node = new Node();
    new_Node->num = num;
    new_Node->next = *head;
    *head = new_Node;    
     size++;
}

int Kth_Node_From_Middle(Node* node, int pos) {
    if(!node)
    return -1;
    Node* ff = node, *ss = node, *mid = NULL;
    int k = 0;
    while(ff && ff->next)
    {
        k++;
        ss = ss->next;
        ff = ff->next->next;
    }
    if(pos > k)
    return -1;
    mid = ss;
    ff = node, ss = node;
    for(int i = 0; i < pos; i++)
    {
        ff = ff->next;
    }
    while(ff != mid)
    {
        ss = ss->next;
        ff = ff->next;
    }
    return ss->num;
}

  //Display all nodes
  void display_all_nodes(Node* node)
    { 
      while(node!=NULL){
        cout << node->num << " "; 
        node = node->next; 
    } 
}

int main()
{
    Node* head = NULL;
    insert(&head,1);
    insert(&head,3);
    insert(&head,5);
    insert(&head,7);
    insert(&head,9);
    cout << "Original list:\n";
    display_all_nodes(head); 
    int pos = 2;
    cout << "\nkth node of a linked list by starting at \nthe middle and moving towards the head:";
    cout << "\nPosition = " << pos;
    int result = Kth_Node_From_Middle(head, pos);
    cout << "\nValue = " << result;
    cout<<endl;
    return 0;
}

Sample Output:

Original list:
9 7 5 3 1
kth node of a linked list by starting at
the middle and moving towards the head:
Position = 2
Value = 9

Flowchart:

Flowchart: Kth node from the Middle towards Head of a Linked List.
Flowchart: Kth node from the Middle towards Head of a Linked List.

CPP Code Editor:

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Previous C++ Exercise: Delete the nth node of a Singly Linked List from end.
Next C++ Exercise: Create and display a doubly linked list.

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C++ Programming: Tips of the Day

How to replace all occurrences of a character in string?

std::string doesn't contain such function but you could use stand-alone replace function from algorithm header.

#include <algorithm>
#include <string>

void some_func() {
  std::string s = "example string";
  std::replace( s.begin(), s.end(), 'x', 'y'); // replace all 'x' to 'y'
}

Ref: https://bit.ly/3niU71x