A list implementation in C

list

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

typedef int elementType;

typedef struct Node {
    elementType d;
    Node* next;
} Node;

void initial(Node **pHead) {
    *pHead = NULL;
    printf("initial success");
}

Node* create(Node* pHead) {

    Node* p1;
    Node* p2;

    p1 = p2 = (Node*)malloc(sizeof(Node));

    if (p1 == NULL || p2 == NULL) {
        printf("malloc fail...");
        exit(0);
    }
    
    memset(p1, 0, sizeof(Node));

    scanf("%d", &p1->d);
    p1->next = NULL;

    while (p1->d > 0) {
        if (pHead == NULL) {
            pHead = p1;
        } else {
            p2->next = p1;
        }

        p2 = p1;
        p1 = (Node*)malloc(sizeof(Node));
        if (p1 == NULL || p2 == NULL) {
            exit(0);
        }
        memset(p1, 0, sizeof(Node));
        scanf("%d", &p1->d);
        p1->next = NULL;
    }

    return pHead;
}

void printList(Node *pHead) {
    if (pHead == NULL) {
        printf("List is empty...");
        exit(0);
    }

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

bool isExistsLoop(Node *pHead) {
    Node *slow = pHead;
    Node *fast = pHead;

    while (fast && fast->next) {
        slow = slow->next;
        fast = fast->next->next;
        if (slow == fast) 
            break;
    }

    return !(fast == NULL || fast->next == NULL);
}

Node* findLoopPort(Node *pHead) {
    Node *slow = pHead;
    Node *fast = pHead;

    while (fast && fast->next) {
        slow = slow->next;
        fast = fast->next->next;

        if (slow == fast)
            break;
    }

    if (fast == NULL || fast->next == NULL) {
        return NULL;
    }

    slow = pHead;
    while (slow != fast) {
        slow = slow->next;
        fast = fast->next;
    }

    return slow;
}

void clearList(Node* pHead) {
    if (pHead == NULL) {
        printf("List is empty");
        return;
    }

    Node *pNext;
    while (pHead != NULL) {
        pNext = pHead->next;
        free(pHead);
        pHead = pNext;
    }
}

int sizeList(Node* pHead) {
    int size = 0;

    while (pHead != NULL) {
        size ++;
        pHead = pHead->next;
    }

    return size;
}

int isEmptyList(Node *pHead) {
    if (pHead == NULL) {
        printf("List is empty");
        return 1;
    }

    return 0;
}

elementType getPosElement(Node *pHead, int pos) {
    int i = 0;

    if (pos < 1) {
        printf("position argument illegal...");
        return 0;
    }

    if (pHead == NULL) {
        printf("List is empty...");
        return 0;
    }

    while (pHead != NULL) {
        ++ i;
        if (i == pos) {
            break;
        }
        pHead = pHead->next;
    }

    if (i < pos) {
        printf("position out of bounds...");
        return 0;
    }

    return pHead->d;
}

elementType *getElementAddr(Node *pHead, elementType x) {
    if (pHead == NULL) {
        printf("List is empty...");
        return NULL;
    }

    if (x < 0) {
        printf("No such element...");
        return NULL;
    }

    while ((pHead->d != x) && (pHead->next != NULL)) {
        pHead = pHead->next;
    }

    if ((pHead != NULL) && (pHead->d != x)) {
        printf("No such element...");
        return NULL;
    }

    return &(pHead->d);
}

int modifyEle(Node *pNode, int pos, elementType x) {
    Node *pHead;
    pHead = pNode;
    int i = 0;

    if (pHead == NULL) {
        printf("List is empty...");
        return 0;
    }

    if (pos < 1) {
        printf("Position argument wrong...");
        return 0;
    }

    while (pHead != NULL) {
        ++ i;
        if (i == pos) {
            break;
        }
        pHead = pHead->next;
    }

    if (i < pos) {
        printf("Position argument wrong...");
        return 0;
    }

    pNode = pHead;
    pNode->d = x;
    return 1;
}