数据结构-线性表-队列

队列的特别实现

组合使用两个栈的后进先出可以实现队列的先进先出，简单高效，入队和出队的时间复杂度可以到 O(1)

SQueue.h

#ifndef _SQUEUE_H_
#define _SQUEUE_H_

typedef void SQueue;

SQueue* SQueue_Create();

void SQueue_Destroy(SQueue* queue);

void SQueue_Clear(SQueue* queue);

int SQueue_Append(SQueue* queue, void* item);

void* SQueue_Retrieve(SQueue* queue);

void* SQueue_Header(SQueue* queue);

int SQueue_Length(SQueue* queue);

#endif

SQueue.c

#include <stdio.h>
#include <malloc.h>
#include "LinkStack.h"
#include "SQueue.h"

typedef struct _tag_SQueue
{
    LinkStack* inStack;
    LinkStack* outStack;
} TSQueue;

SQueue* SQueue_Create() // O(1)
{
    TSQueue* ret = (TSQueue*)malloc(sizeof(TSQueue));

    if( ret != NULL )
    {
        ret->inStack = LinkStack_Create();
        ret->outStack = LinkStack_Create();

        if( (ret->inStack == NULL) || (ret->outStack == NULL) )
        {
            LinkStack_Destroy(ret->inStack);
            LinkStack_Destroy(ret->outStack);

            free(ret);

            ret = NULL;
        }
    }

    return ret;
}

void SQueue_Destroy(SQueue* queue) // O(n)
{
    SQueue_Clear(queue);
    free(queue);
}

void SQueue_Clear(SQueue* queue) // O(n)
{
    TSQueue* sQueue = (TSQueue*)queue;

    if( sQueue != NULL )
    {
        LinkStack_Clear(sQueue->inStack);
        LinkStack_Clear(sQueue->outStack);
    }
}

int SQueue_Append(SQueue* queue, void* item) // O(1)
{
    TSQueue* sQueue = (TSQueue*)queue;

    if( sQueue != NULL )
    {
        LinkStack_Push(sQueue->inStack, item);
    }
}

void* SQueue_Retrieve(SQueue* queue) // O(1)
{
    TSQueue* sQueue = (TSQueue*)queue;
    void* ret = NULL;

    if( sQueue != NULL )
    {
        if( LinkStack_Size(sQueue->outStack) == 0 )
        {
            while( LinkStack_Size(sQueue->inStack) > 0 )
            {
                LinkStack_Push(sQueue->outStack, LinkStack_Pop(sQueue->inStack));
            }
        }

        ret = LinkStack_Pop(sQueue->outStack);
    }

    return ret;
}

void* SQueue_Header(SQueue* queue) // O(1)
{
    TSQueue* sQueue = (TSQueue*)queue;
    void* ret = NULL;

    if( sQueue != NULL )
    {
        if( LinkStack_Size(sQueue->outStack) == 0 )
        {
            while( LinkStack_Size(sQueue->inStack) > 0 )
            {
                LinkStack_Push(sQueue->outStack, LinkStack_Pop(sQueue->inStack));
            }
        }

        ret = LinkStack_Top(sQueue->outStack);
    }

    return ret;
}

int SQueue_Length(SQueue* queue) // O(1)
{
    TSQueue* sQueue = (TSQueue*)queue;
    int ret = -1;

    if( sQueue != NULL )
    {
        ret = LinkStack_Size(sQueue->inStack) + LinkStack_Size(sQueue->outStack);
    }

    return ret;
}

main.c

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

/* run this program using the console pauser or add your own getch, system("pause") or input loop */

int main(int argc, char *argv[])
{
    SQueue* queue = SQueue_Create();
    int a[10] = {0};
    int i = 0;

    for(i=0; i<10; i++)
    {
        a[i] = i + 1;

        SQueue_Append(queue, a + i);
    }

    printf("Header: %d\n", *(int*)SQueue_Header(queue));
    printf("Length: %d\n", SQueue_Length(queue));

    for(i=0; i<5; i++)
    {
        printf("Retrieve: %d\n", *(int*)SQueue_Retrieve(queue));
    }

    printf("Header: %d\n", *(int*)SQueue_Header(queue));
    printf("Length: %d\n", SQueue_Length(queue));

    for(i=0; i<10; i++)
    {
        a[i] = i + 1;

        SQueue_Append(queue, a + i);
    }

    while( SQueue_Length(queue) > 0 )
    {
        printf("Retrieve: %d\n", *(int*)SQueue_Retrieve(queue));
    }

    SQueue_Destroy(queue);

    return 0;
}