GFG PTOD | 21 Jan 2025 | Linked List Group Reverse

Recursive Solution :

Node *reverseKGroup(Node *head, int k) {
        // code here
        // Recursive
        struct Node* cur = head, *prev = NULL, *next = NULL;
        int count = 0;
        while(cur != NULL && count < k) {
            next = cur->next;
            cur->next = prev;
            prev = cur;
            cur = next;
            count++;
        }
        if(next) head->next = reverseKGroup(next, k);
        return prev;
    }

Iterative Solution :

Node *reverseKGroup(Node *head, int k) {
        // code here
        // Iterative
        struct Node* cur = head, *newHead = NULL, *tail=NULL;
        while(cur) {
            struct Node* cur1 = cur, *prev = NULL, *next = NULL;
            int count = 0;
            while(cur != NULL && count < k) {
                next = cur->next;
                cur->next = prev;
                prev = cur;
                cur = next;
                count++;
            }
            if(newHead == NULL) newHead = prev;
            if(tail) tail->next = prev;
            tail = cur1;
        }
        
        return newHead;
    }