栈和队列4--循环队列（标志位）

解决假溢出问题，1，少用一个元素，
判断满的条件：（Q.rear+1)% MaxSize==Q.front
2.设置标志位（现在来定）
判断满：
if (Q.tag = = 1 && (Q.rear = = Q.front))
判断空：
if (Q.tag = = 0 && (Q.rear = = Q.front))

#include<iostream>
#define//循环队列最大长度
using namespace std;

typedef  int QElemType;//数据类型
typedef struct {
  QElemType *base;
  int front;//头指针
  int rear;//尾指针
  int tag;//标志位
}SqQueue;

//1.初始化,队空条件：front=rear=0
bool InitQueue(SqQueue &Q) {
  //空队列
  Q.base = new QElemType[MaxSize];
  Q.base = (int*)malloc(MaxSize * sizeof(int));
  if (!Q.base)  return false;
  Q.front = Q.rear = 0;
  Q.tag = 0;
  return true;
}

//2.入列

bool EnQueue(SqQueue & Q, QElemType e) {
  if (Q.tag = =  1  &&  (Q.rear = = Q.front)) return false;//判断循环队满
  Q.base[Q.rear] = e;
  Q.rear = (Q.rear + 1)%MaxSize;//队尾加1
  if (Q.tag == 0)
    Q.tag = 1;//表示队列非空
  return true;
}

//3.队长度

int QueueLength(SqQueue Q) {
  return (Q.rear + MaxSize - Q.front) % MaxSize;
}

//4.出队列,删除头元素

bool DeQueue(SqQueue &Q, QElemType &e) {
  **if (Q.tag = = 0&&Q.front = = Q.rear)  return false;//判空**
  e = Q.base[Q.front];
  Q.front = (Q.front + 1) % MaxSize;
  if (Q.tag == 1)
    Q.tag = 0;//表示队列非满
  return true;
}

//5.取头元素

GetTop(SqQueue Q) {
  if (Q.tag == 0 && Q.front == Q.rear)
    return NULL;//判空
  else
    return Q.base[Q.front];
}

bool isEmpyt(SqQueue Q) {
  return Q.tag == 0 && Q.front == Q.rear;
}

//6.遍历

void ShowQueue(SqQueue Q) {
  QElemType e;
  while (!isEmpyt(Q)) {
    DeQueue(Q, e);
    cout << e << " ";
  }cout << endl;
}

int main() {
  SqQueue  S; QElemType e;
  if (InitQueue(S))cout << "Succeed" << endl;
  else cout << "Failed" << endl;
  //入栈
  cout << "input e:\t";
  while (cin >> e) {//按"ctrl+z"结束输入
    EnQueue(S, e);
    cout << "input e:\t";
  }
  cout << "栈顶元素为" << GetTop(S) << endl;
  cout << "栈所有元素为" << endl;
  ShowQueue(S);
  cout << "栈长度为" << QueueLength(S) << endl;
  //出栈
  if (DeQueue(S, e))
    cout << "移除的头元素是" << e << endl;
  else cout << "栈空" << endl;
  cout << "栈剩下所有元素为" << endl;
  ShowQueue(S);
  cout << "栈长度为" << QueueLength(S) << endl;
}