Remove Nth Node From End of List #leetcode #c

remove_nth_node_from_end_of_list.c

#include <stdio.h>
#include <stdlib.h>

struct ListNode {
    int val;
    struct ListNode *next;
};

struct ListNode* createNodeList(int arr[], int numSize);
struct ListNode* removeNthFromEnd(struct ListNode* head, int n);
void displayList();

void main() {
    struct ListNode *head;

    int arr[] = {1, 2, 3, 4, 5};

    head = createNodeList(arr, (sizeof(arr) / sizeof(*arr)));

    displayList(head);

    head = removeNthFromEnd(head, 2);
    printf("\n");

    displayList(head);
}

struct ListNode* createNodeList(int arr[], int numSize) {
    struct ListNode *head, *previous, *current;
    head = previous = current = (struct ListNode *) malloc(sizeof(struct ListNode));

    previous->val = arr[0];
    previous->next = NULL;

    for (int i = 1; i < numSize; i++, previous = previous->next) {
        current = (struct ListNode *) malloc(sizeof(struct ListNode));
        current->val = arr[i];
        current->next = NULL;
        previous->next = current;
    }

    return head;
}

struct ListNode* removeNthFromEnd(struct ListNode* head, int n) {
    struct ListNode *fast = head;
    struct ListNode *slow = head;
    int i = 0;

    while (fast->next != NULL) {
        if (i >= n) {
            slow = slow->next;
        }
        fast = fast->next;
        i++;
    }

    if (i < n) {
        head = head->next;
    } else {
        slow->next = slow->next->next;
    }

    return head;
}

void displayList(struct ListNode *head) {
    struct ListNode *tmp;
    tmp = head;

    while(tmp != NULL) {
        printf("%d, ", tmp->val);
        tmp = tmp->next;
    }
}