之前用习惯了面向对象的调用方式，用C写过程的还是有点不习惯，不过管用就行。

队列的操作很简单：

1、先进先出

2、入队的时候要检测队列是否已满；

3、出队列的时候要检测是否为空；

#include <iostream>
#include <memory>
#include "stdio.h"
#include "malloc.h"

typedef int ElementType;
#define CheckNULLQueue(Q) if ((Q) == NULL)							printf("queue is null\n"); 							return 

struct QueueRecord{
	int Capacity;
	int Size;
	int Front;
	int Rear;
	ElementType* Array;
}; 

typedef QueueRecord* Queue;

bool IsEmpty(Queue Q){
	if (NULL == Q){
		return false;
	}
	return Q->Size == 0;
}

bool IsFull(Queue Q){
	if (NULL == Q){
		return false;
	}
	
	return Q->Size == Q->Capacity;
}

void MakeEmptyQueue(Queue Q){
	if (NULL == Q){
		return;
	}
	
	Q->Size = 0;
	Q->Front = 1;
	Q->Rear = 0;
}

Queue CreateQueue(int maxElements){
	if (maxElements < 0){
		printf("error\n");
		return NULL;
	}
	
	Queue q = (Queue)malloc(sizeof(QueueRecord));
	if (NULL == q){
		printf("malloc error\n");
		return NULL;
	}
	q->Capacity = maxElements;
	
	MakeEmptyQueue(q);
	
	q->Array = (ElementType*)malloc(maxElements * sizeof(ElementType));
	if (q->Array == NULL){
		printf("error\n");
		free(q);
		return NULL;
	}
	
	return q;
}

void Enqueue(ElementType X, Queue Q){
	if (Q == NULL){
		printf("Q is null\n");
		return;
	}
	
	if (IsFull(Q)){
		printf("Q is full with enqueue element:%d\n", X);
		return;
	}
	
	++Q->Size;
	Q->Rear = (Q->Rear + 1) % Q->Capacity;
	Q->Array[Q->Rear] = X;
}

ElementType Front(Queue Q){
	if (IsEmpty(Q)){
		printf("Front error\n");
		return -1;
	}
	
	return Q->Array[Q->Front];
}

void Dequeue(Queue Q){
	if (IsEmpty(Q)){
		printf("Dequeue is empty\n");
		return ;
	}
	
	--Q->Size;
	Q->Front = (Q->Front + 1) % Q->Capacity;
} 

ElementType FrontAndDequeue(Queue Q){
	if (IsEmpty(Q)){
		printf("FrontAndDequeue error with queue is empty\n");
		return -1;
	}
	
	ElementType res = Q->Array[Q->Front];
	
	--Q->Size;
	Q->Front = (Q->Front + 1) % Q->Capacity;
	
	return res;
}
int main(){
	int num = 3;
	Queue pQueue = CreateQueue(num);
	if (NULL == pQueue){
		printf("CreateQueue failed\n");
		return 0;
	}
	Dequeue(pQueue);
	Enqueue(1, pQueue);
	Enqueue(2, pQueue);
	Enqueue(3, pQueue);
	Enqueue(4, pQueue);
	
	printf("front:%d\n", FrontAndDequeue(pQueue));
	
	Dequeue(pQueue);
	Dequeue(pQueue);
	Dequeue(pQueue);
	Dequeue(pQueue);
	Dequeue(pQueue);
	
	printf("front:%d\n", Front(pQueue));
}

队列简单实现