Double LinkList

#include "stdio.h"
#include "malloc.h"

struct Node{
    int value;
    Node *next, *prev;
}*head, *tail, *current;

Node* createNode(int value){
    Node* temp  = (Node*)malloc(sizeof(Node));
    temp->value = value;
    temp->prev = temp->next  = NULL;

    return temp;
}

int TOTAL_DATA = 0;

void pushHead(int value){
    current = createNode(value);
    if( !head ){
        head = tail = current;
    }else{
        current->next = head;
        head->prev = current;
        head = current;
    }
    ++TOTAL_DATA;
}

void pushTail(int value){
    current = createNode(value);
    if( !head ){
        head = tail = current;
    }else{
        tail->next = current;
        current->prev = tail;
        tail = current;
    }
    ++TOTAL_DATA;
}

void pushMidByIndex(int index, int value){
    if( index < 0 || index > TOTAL_DATA ) return;
    if( index == 0 ) pushHead(value);
    else if( index == TOTAL_DATA ) pushTail(value);
    else{
        Node* find = head;
        current = createNode(value);
        for(int i=1;i<index;++i) find = find->next;

        current->next = find->next;
        find->next->prev = current;
        find->next = current;
        current->prev = find;
        ++TOTAL_DATA;
    }
}

void popHead(){
    if( !head ) return;
    if( head == tail ){
        free(head);
        head = tail = NULL;
        --TOTAL_DATA;
        return;
    }
    current = head;
    head = head->next;
    free(current);
    head->prev = current = NULL;
    --TOTAL_DATA;;
}

void popTail(){
    if( !head ) return;
    if( head == tail ){
        free(head);
        head = tail = NULL;
        --TOTAL_DATA;
        return;
    }
    current = tail;
    tail = tail->prev;
    free(current);
    tail->next = current = NULL;
    --TOTAL_DATA;
}

void popMidByIndex(int index){
    if( index < 0 || index > TOTAL_DATA-1 ) return;
    if( head == tail ){
        free(head);
        head = tail = NULL;
        --TOTAL_DATA;
        return;
    }

    Node* find = head;
    for(int i = 0 ; i < index; ++i) find = find->next;

    find->prev->next = find->next;
    find->next->prev = find->prev;
    free(find);
    find = NULL;
    --TOTAL_DATA;
}

void popAll(){
    while( head ) popHead();
}

int viewAll(){
    current = head;
    while( current ){
        printf("%d ", current->value);
        current = current->next;
    }
}

int main(){
    pushMidByIndex(0,1);
    pushMidByIndex(0,2);
    pushMidByIndex(0,3);
    pushMidByIndex(0,4);
    pushMidByIndex(0,5);
    popMidByIndex(2);
    pushMidByIndex(2,100);
    viewAll();
    getchar();
    return 0;
}