按客户类型实现队列进出：修改LIST/OUT命令及解决实现异常

Hey there! Let's work through your queue problem together. First, let's fix the garbled text issue in your current dual-queue setup, then I'll show you a solid alternative using a single queue with priority handling.

First, let's diagnose why your current code is showing messed-up card numbers and customer types:

• Wrong data type for CardNum: You declared CardNum as an int, but tried to use strcpy (a string function) on it. Card numbers often have leading zeros or are too long for integers, so it should be a character array instead.
• Mistaken strcpy calls: In your Enqueue function, you copied both the card number and customer type to temp->CardNum, leaving temp->CustomerType uninitialized (hence the garbled text).
• Uninitialized queues: You never set q1.front, q1.rear, q2.front, q2.rear to NULL at the start, which can cause undefined behavior.

Here's the corrected dual-queue code that meets your requirements:

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

// Global counter for sequential record numbers
int global_record = 1;

typedef struct Node {
    int record;
    char CardNum[20];  // Changed to char array for valid card storage
    char CustomerType[20];
    struct Node* next;
} Node;

typedef struct queue {
    Node* front;
    Node* rear;
} Queue;

Queue q1, q2;  // q1 = VIP queue, q2 = Ordinary queue

void Enqueue(Queue *q, char *card, char *type);
void List();
void Out();

int main() {
    char command[10];
    char card[20], client[20];

    // Initialize queues to empty state
    q1.front = q1.rear = NULL;
    q2.front = q2.rear = NULL;

    while(1) {
        scanf("%s", command);
        if(strcmp(command,"IN") == 0) {
            printf("IN: ");
            scanf("%s %s", card, client);
            if(strcmp(client,"VIP") == 0) {
                Enqueue(&q1, card, client);
            } else if(strcmp(client,"Ordinary") == 0) {
                Enqueue(&q2, card, client);
            }
        } else if(strcmp(command,"LIST") == 0) {
            printf("LIST:\n");
            List();
        } else if(strcmp(command,"OUT") == 0) {
            printf("OUT:\n");
            Out();
        } else if(strcmp(command,"QUIT") ==0) {
            printf("GOOD BYE!\n");
            break;
        }
    }
    return 0;
}

void Enqueue(Queue *q, char *card, char *type) {
    Node* temp = (Node*)malloc(sizeof(Node));
    if (!temp) {
        printf("Memory allocation failed!\n");
        return;
    }
    temp->record = global_record++;
    strcpy(temp->CardNum, card);
    strcpy(temp->CustomerType, type);
    temp->next = NULL;

    if(q->front == NULL && q->rear == NULL) {
        q->front = q->rear = temp;
    } else {
        q->rear->next = temp;
        q->rear = temp;
    }
    printf("Enqueued: %d %s %s\n", temp->record, temp->CardNum, temp->CustomerType);
}

void List() {
    // Print all VIP customers first (in enqueue order)
    Node *temp = q1.front;
    while(temp != NULL) {
        printf("%d %s %s\n", temp->record, temp->CardNum, temp->CustomerType);
        temp = temp->next;
    }
    // Then print all Ordinary customers
    temp = q2.front;
    while(temp != NULL) {
        printf("%d %s %s\n", temp->record, temp->CardNum, temp->CustomerType);
        temp = temp->next;
    }
}

void Out() {
    // Prioritize VIP queue for dequeue
    if (q1.front != NULL) {
        Node *temp = q1.front;
        printf("%d %s %s\n", temp->record, temp->CardNum, temp->CustomerType);
        q1.front = q1.front->next;
        // Update rear if queue becomes empty
        if (q1.front == NULL) {
            q1.rear = NULL;
        }
        free(temp);
    } else if (q2.front != NULL) {
        Node *temp = q2.front;
        printf("%d %s %s\n", temp->record, temp->CardNum, temp->CustomerType);
        q2.front = q2.front->next;
        if (q2.front == NULL) {
            q2.rear = NULL;
        }
        free(temp);
    } else {
        printf("Queue is empty!\n");
    }
}

If you prefer not to use two separate queues, you can use a single queue where each node tracks its customer type. Here's how to implement the required behavior:

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

int global_record = 1;

typedef struct Node {
    int record;
    char CardNum[20];
    char CustomerType[20];
    struct Node* next;
} Node;

typedef struct queue {
    Node* front;
    Node* rear;
} Queue;

Queue q;

void Enqueue(char *card, char *type);
void List();
void Out();

int main() {
    char command[10];
    char card[20], client[20];

    q.front = q.rear = NULL;

    while(1) {
        scanf("%s", command);
        if(strcmp(command,"IN") == 0) {
            printf("IN: ");
            scanf("%s %s", card, client);
            Enqueue(card, client);
        } else if(strcmp(command,"LIST") == 0) {
            printf("LIST:\n");
            List();
        } else if(strcmp(command,"OUT") == 0) {
            printf("OUT:\n");
            Out();
        } else if(strcmp(command,"QUIT") ==0) {
            printf("GOOD BYE!\n");
            break;
        }
    }
    return 0;
}

void Enqueue(char *card, char *type) {
    Node* temp = (Node*)malloc(sizeof(Node));
    if (!temp) {
        printf("Memory allocation failed!\n");
        return;
    }
    temp->record = global_record++;
    strcpy(temp->CardNum, card);
    strcpy(temp->CustomerType, type);
    temp->next = NULL;

    if(q.front == NULL && q.rear == NULL) {
        q.front = q.rear = temp;
    } else {
        q.rear->next = temp;
        q.rear = temp;
    }
    printf("Enqueued: %d %s %s\n", temp->record, temp->CardNum, temp->CustomerType);
}

void List() {
    // First print all VIP customers (maintaining enqueue order)
    Node *temp = q.front;
    while(temp != NULL) {
        if (strcmp(temp->CustomerType, "VIP") == 0) {
            printf("%d %s %s\n", temp->record, temp->CardNum, temp->CustomerType);
        }
        temp = temp->next;
    }
    // Then print all Ordinary customers
    temp = q.front;
    while(temp != NULL) {
        if (strcmp(temp->CustomerType, "Ordinary") == 0) {
            printf("%d %s %s\n", temp->record, temp->CardNum, temp->CustomerType);
        }
        temp = temp->next;
    }
}

void Out() {
    if (q.front == NULL) {
        printf("Queue is empty!\n");
        return;
    }

    // Dequeue front if it's VIP
    if (strcmp(q.front->CustomerType, "VIP") == 0) {
        Node *temp = q.front;
        printf("%d %s %s\n", temp->record, temp->CardNum, temp->CustomerType);
        q.front = q.front->next;
        if (q.front == NULL) q.rear = NULL;
        free(temp);
        return;
    }

    // Find and dequeue the first VIP in the queue
    Node *prev = q.front;
    Node *curr = q.front->next;
    while (curr != NULL) {
        if (strcmp(curr->CustomerType, "VIP") == 0) {
            printf("%d %s %s\n", curr->record, curr->CardNum, curr->CustomerType);
            prev->next = curr->next;
            if (curr == q.rear) q.rear = prev;
            free(curr);
            return;
        }
        prev = curr;
        curr = curr->next;
    }

    // No VIPs left, dequeue front ordinary node
    Node *temp = q.front;
    printf("%d %s %s\n", temp->record, temp->CardNum, temp->CustomerType);
    q.front = q.front->next;
    if (q.front == NULL) q.rear = NULL;
    free(temp);
}

Key Notes for the Single Queue Approach #

• LIST: Traverses the queue twice to separate VIP and ordinary entries, keeping their original enqueue order intact within each group.
• OUT: Checks for a VIP at the front first; if none exists, it searches for the first VIP in the queue to dequeue. Only when no VIPs are left does it dequeue an ordinary customer.

Both implementations fulfill your requirements:

• LIST outputs VIP customers first (in ascending order of their queue entry), followed by ordinary customers.
• OUT always prioritizes VIP customers for dequeuing.

内容的提问来源于stack exchange，提问作者Zuher Abud