c/c++线性循环队列

线性循环队列

队列是先进先出，和栈相反.

线性循环队列，牺牲一个空间，实现循环。比如空间大小为4，牺牲一个空间，所以最多放3个元素。

假设front指向0位置，tail指向3位置

1	2	3	空

出队后

front指向1位置，tail位置不变还是3

空	2	3	空

入队后（4）

front指向不变还是1，tail指向0位置

空	2	3	4

出队后

front指向2位置，tail位置不变还是0

空	空	3	4

入队后（5）

front指向不变还是2，tail指向1位置

5	空	3	4

whilequeue.h

#ifndef __WHILEQUEUE__
#define __WHILEQUEUE__

#include <stdio.h>
#include <malloc.h>
#include <assert.h>
#include <memory.h>
#include <stdbool.h>

#define WHILEQUEUE_INIT_SIZE 8

typedef int ElemType;

typedef struct whilequeue{
  ElemType* base;
  int front;
  int tail;
}whilequeue;

void init(whilequeue*);
//入队
void enQueue(whilequeue*, ElemType);
void show_list(whilequeue*);
//出队
void deQueue(whilequeue*);
void clear(whilequeue*);
void destroy(whilequeue*);
#endif

whilequeue.c

#include "whilequeue.h"

void init(whilequeue* seq){
  seq->base = (ElemType*)malloc(sizeof(ElemType) * WHILEQUEUE_INIT_SIZE);
  seq->front = seq->tail = 0;
}
void enQueue(whilequeue* seq, ElemType x){
  //判断队列是否已满
  if((seq->tail + 1) % WHILEQUEUE_INIT_SIZE == seq->front){
    printf("queue is full\n");
    return;
  }
  seq->base[seq->tail] = x;
  seq->tail = (seq->tail + 1) % WHILEQUEUE_INIT_SIZE;
}
void show_list(whilequeue* seq){
  int i = seq->front;
  while(i != seq->tail){
    printf("%d\n", seq->base[i++ % WHILEQUEUE_INIT_SIZE]);
    i = i % WHILEQUEUE_INIT_SIZE;
  }
}
void deQueue(whilequeue* seq){
  //判断队列是否为空，空了的话，就不需要移动front
  if(seq->front == seq->tail)return;
  seq->front = (seq->front + 1) % WHILEQUEUE_INIT_SIZE;
}
void clear(whilequeue* seq){

}
void destroy(whilequeue* seq){

}

whilequeuemain.c

#include "whilequeue.h"

int main(){
  whilequeue list;
  init(&list);
  int select = 1;
  ElemType item;
  int index;
  while(select){
    printf("*****************************************\n");
    printf("*** [1]   push        [2]  pop        ***\n");
    printf("*** [3]   show_list   [4]  length     ***\n");
    printf("*** [5]   clear       [6]  destroy    ***\n");
    printf("*** [0]   quit                        ***\n");
    printf("*****************************************\n");
    printf("请选择:>");
    scanf("%d", &select);
    if(0 == select)
      break;
    switch(select){
    case 1:
      printf("请输入要插入的数据>\n");
      scanf("%d",&item);
      enQueue(&list, item);
      show_list(&list);
      break;
    case 2:
      deQueue(&list);
      show_list(&list);
      break;
    case 3:
      show_list(&list);
      break;
    case 5:
      clear(&list);
      show_list(&list);
      break;
    case 6:
      destroy(&list);
      break;
    default:
      printf("输入的选择错误，请重新选择\n");
      break;
    }
  }
  //destroy(&list);
}