Reverse List

list.c

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

struct list {
    struct list *next;
    int n;
};

struct list *new_list(int *arr, size_t n) {
    struct list *ret = NULL, *ptr = NULL;
    for(size_t i = 0 ; i < n ; ++i) {
        if(ptr == NULL) {
            ptr = calloc(1, sizeof(struct list));
        } else {
            ptr->next = calloc(1, sizeof(struct list));
            ptr = ptr->next;
        }
        if(ret == NULL) {
            ret = ptr;
        }
        ptr->n = arr[i];
    }
    return ret;
}

void delete_list(struct list *head) {
    for(struct list *it = head ; it != NULL ; ) {
        struct list *tmp = it->next;
        free(it);
        it = tmp;
    }
}

void print_list(struct list *head) {
    for(struct list *it = head ; it != NULL ; it = it->next) {
        printf("%d ", it->n);
    }
}

/*
 * @return reversed head 
 */
struct list *reverse_list(struct list *head) {
    struct list *prev = NULL, *it = head;
    while(it != NULL) {
        struct list *tmp = it->next;
        it->next = prev;
        prev = it;
        it = tmp;
    }
    return prev;
}

int main(){
    int arr[] = {1, 2, 3, 4, 5};
    struct list *l = new_list(arr, sizeof(arr) / sizeof(*arr));
    print_list(l);
    printf("\n");
    l = reverse_list(l);
    print_list(l);
    printf("\n");
    delete_list(l);
    return 0;
}