C語言查詢雙向連結串列中資料項程式

建立一個雙向連結串列，並查詢此雙向連結串列中的資料項的範例程式，將以下程式碼儲存到一個原始檔中：search_doubly_linked_list.c， 如下所示 -

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

struct node {
    int data;
    struct node *prev;
    struct node *next;
};

struct node *head = NULL;
struct node *last = NULL;

struct node *current = NULL;

//display the list
void printList() {
    struct node *ptr = head;

    printf("\n[head] <=>");
    //start from the beginning
    while (ptr != NULL) {
        printf(" %d <=>", ptr->data);
        ptr = ptr->next;
    }

    printf(" [last]\n");
}


//Create Linked List
void insert(int data) {
    // Allocate memory for new node;
    struct node *link = (struct node*) malloc(sizeof(struct node));

    link->data = data;
    link->prev = NULL;
    link->next = NULL;

    // If head is empty, create new list
    if (head == NULL) {
        head = link;
        return;
    }

    current = head;

    // move to the end of the list
    while (current->next != NULL)
        current = current->next;

    // Insert link at the end of the list
    current->next = link;
    last = link;
    link->prev = current;
}


void search(int data) {
    int pos = 0;

    if (head == NULL) {
        printf("Linked List not initialized");
        return;
    }

    current = head;
    while (current != NULL) {
        pos++;
        if (current->data == data) {
            printf("%d found at position %d\n", data, pos);
            return;
        }

        if (current->next != NULL)
            current = current->next;
        else
            break;
    }

    printf("%d does not exist in the list\n", data);
}


int main() {
    insert(10);
    insert(20);
    insert(30);
    insert(40);
    insert(50);
    insert(60);

    printList();
    search(6);
    search(50);

    return 0;
}

執行上面程式，得到以下結果 -

[head] <=> 10 <=> 20 <=> 30 <=> 40 <=> 50 <=> 60 <=> [last]
6 does not exist in the list
50 found at position 5