循环队列加入tag使front==rear用做队满条件

#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#define maxsize 100
using namespace std;

typedef struct {
  int data[maxsize];
  int front,rear;
  int tag;
}squeue;
int desqueue(squeue &sq,int &x)
{
    if(sq.front==sq.rear&&sq.tag==0) return 0;
    else
    {
        x=sq.data[sq.front];
        sq.front=(sq.front+1)%maxsize;
        if(sq.rear==sq.front) sq.tag=0;
        return 1;
    }
}
int ensqueue(squeue &sq,int x)
{
    if(sq.front==sq.rear&&sq.tag==1) return 0;
    else
    {
        sq.data[sq.rear]=x;
        sq.rear=(sq.rear+1)%maxsize;
        if(sq.rear==sq.front) sq.tag=1;
        return 1;
    }
}
int main()
{
    squeue sq;
    sq.front=0;
    sq.rear=0;
    sq.tag=0;
    int x=0;
    ensqueue(sq,3);
    desqueue(sq,x);
    printf("%d",x);
    return 0;
}