c - 队列实现

Question

#include<stdio.h>
#include<stdlib.h>
#include<malloc.h>
#include "Mission6.h"
/************************************************************************
* function name:MissionSix
* input:none
* output:none
* operation:gets a choice from the user makes a menu to choose from.
*************************************************************************/ 
void MissionSix(){
    static int queueTail=0,queueHead=0,amountOfTimes=0; //so their values stay throughout the program.
    //amountOfItems represents the amount of times i used the functionAddItemToQueue
    int choice;
    int **queue=NULL;
    PrintMenu();
    do{
        scanf("%d",&choice);
        switch(choice){
            case 0: 
                return;
            case 1:
                AddItemToQueue(queue,&queueHead,&queueTail,&amountOfTimes);
                break;
            case 2:
                RemoveItemFromQueue(queue,&queueHead,&queueTail);
                break;
            case 3:
                PrintQueue(queue,&queueHead,&queueTail);
                break;
            case 4:
                break;
            case 5:
                break;
            case 6:
                break;
            case 7:
                break;
            case 8: 
                PrintMenu();
                break;
            default:
                printf("Error: Unrecognized choice\n");
        }
        printf("Please select your next choice (select 8 for complete menu)\n");
    } //end of "do"
    while(choice!=0);

}
/************************************************************************
* function name:printMenu
* input:none
* output:none
* operation:prints the menu.
*************************************************************************/ 
void PrintMenu(){ 
    printf("Please select your choice:\n");
    printf("0. Exit\n");
    printf("1. Add item to the queue\n");
    printf("2. Remove item from the queue\n");
    printf("3. Print queue\n");
    printf("4. Print the maximum item in the queue\n");
    printf("5. Print the minimum item in the queue\n");
    printf("6. Print index of given item\n");
    printf("7. Clear queue\n");
    printf("8. Print the menu\n");
}
/************************************************************************
* function name:AddItemToQueue
* input: the queue (an array of pointers), its head(integer), its tail(int) and the amount
  of times this function was called(int)
* output:none
* operation:gets an item from the user and adds it to the queue.
*************************************************************************/ 
void AddItemToQueue(int **queue,int *head,int* tail,int* amountOfTimes){
    int itemToAdd;
    printf("Enter item value to add \n");
    scanf("%d",&itemToAdd);
    queue=(int **)realloc(queue,sizeof(int*)*((*amountOfTimes)+1)); //amount of items in queue =*head - *tail
    if(queue==NULL){
        printf("Error: Insufficient Memory\n");
        return;
    }
    queue[*head]=(int *)malloc(sizeof(int)); //builds size for the data
    if (queue[*head]==NULL){
        printf("Error: Insufficient Memory\n");
        return;
    }
    *queue[*head]=itemToAdd;//adding the item to the correct spot
    (*head)++;
    (*amountOfTimes)++;
}
/************************************************************************
* function name:RemoveItemFromQueue
* input:the queue (an array of pointers), its head(integer) and its tail(int). 
* output:none
* operation:removes first element in the queue.
*************************************************************************/ 
void RemoveItemFromQueue(int **queue,int *head, int* tail){
    if((*head)==(*tail)){ //if head and tail are equal the queue is empty.
        printf("Error: Queue is empty!\n");
        return;
    }

    free(queue[*tail]);
    (*tail)++;
}
/************************************************************************
* function name:PrintQueue
* input:the queue (an array of pointers), its head(integer) and its tail(int). 
* output:none
* operation:prints the elements of the queue
*************************************************************************/ 
void PrintQueue(int **queue,int *head, int*tail){
    int i;
    printf("Queue items are: ");
    for(i=(*tail);i<(*head);i++){
        printf("%d ",**(queue+i));
    }
}

我想要做的是在 c 中实现一个队列：它作为先入先出的方式工作。

问题是：

1. “RemoveItemFromQueue”功能不起作用
2. “PrintQueue”函数由于某种原因无法工作。

请注意，我知道我的程序中没有释放 malloc，稍后再处理。

Answer 1

试试这个（如果我的理解有误，我很抱歉）：

#include <stdio.h>
#include <stdlib.h>
//#include "Mission6.h"
void PrintMenu(void);
void AddItemToQueue(int **queue,int *head,int* tail,int* amountOfTimes);
void RemoveItemFromQueue(int **queue,int *head, int* tail);
void PrintQueue(int *queue, int head, int tail);

void MissionSix(void){
    int queueTail = 0, queueHead = 0, amountOfTimes = 0;
    //amountOfItems represents the amount of times i used the functionAddItemToQueue
    int choice;
    int *queue = NULL;
    PrintMenu();
    do{
        scanf("%d", &choice);
        switch(choice){
        case 0:
            free(queue);
            return;
        case 1:
            AddItemToQueue(&queue, &queueHead, &queueTail, &amountOfTimes);
            break;
        case 2:
            RemoveItemFromQueue(&queue, &queueHead, &queueTail);
            break;
        case 3:
            PrintQueue(queue, queueHead, queueTail);
            break;
        case 4:
            break;
        case 5:
            break;
        case 6:
            break;
        case 7:
            break;
        case 8: 
            PrintMenu();
            break;
        default:
            printf("Error: Unrecognized choice\n");
        }
        printf("Please select your next choice (select 8 for complete menu)\n");
    } while(choice != 0);

}

void PrintMenu(void){ 
    fputs(
        "Please select your choice:\n"
        "0. Exit\n"
        "1. Add item to the queue\n"
        "2. Remove item from the queue\n"
        "3. Print queue\n"
        "4. Print the maximum item in the queue\n"
        "5. Print the minimum item in the queue\n"
        "6. Print index of given item\n"
        "7. Clear queue\n"
        "8. Print the menu\n",
        stdout
    );
}

void AddItemToQueue(int **queue, int *head, int *tail, int *amountOfTimes){
    int itemToAdd;
    printf("Enter item value to add \n");
    scanf("%d", &itemToAdd);
    *queue = realloc(*queue, ++*amountOfTimes * sizeof(int));
    if(*queue == NULL){
        printf("Error: Insufficient Memory\n");
        return;
    }
    (*queue)[(*tail)++] = itemToAdd;
}

void RemoveItemFromQueue(int **queue, int *head, int *tail){
//if restructure queue, need int *amountOfTimes
    if( *head == *tail){
        printf("Error: Queue is empty!\n");
        return;
    }
    ++*head;
}

void PrintQueue(int *queue, int head, int tail){
    int i;
    printf("Queue items are: ");
    for(i = head; i < tail; ++i){
        printf("%d ", queue[i]);
    }
    puts("");
}

int main(void){
    MissionSix();
}