题解 | #【模板】循环队列#

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
typedef struct
{
    int* data;
    int front;
    int back;
    int capacity;//空间容量 = 固定长度 + 1 = n + 1，多开一个方便判空、判满
}cirQueue;
void QueueInit(cirQueue* obj,int n)
{
    obj->data = (int*)malloc(sizeof(int) * (n + 1));
    obj->front = obj->back = 0;
    obj->capacity = n + 1;
}
bool QueueIsFull(cirQueue* obj)
{
    //back尾的下一个是front头就是满了
    return (obj->back + 1) % obj->capacity == obj->front;
}
bool QueueIsEmpty(cirQueue* obj)
{
    return obj->front == obj->back;
}
bool QueuePush(cirQueue* obj,int x)
{
    if (QueueIsFull(obj))
    {
        return false;
    }

    obj->data[obj->back++] = x;
    //注意边界
    //模等一下置为有效范围
    obj->back %= obj->capacity;
    return true;
}
//empty传址用来判断循环队列是不是空
int QueueFront(cirQueue* obj,int* empty)
{
    if (QueueIsEmpty(obj))
    {
        *empty = 1;
        return 0;
    }
    return obj->data[obj->front];
}
int QueuePop(cirQueue* obj,int* empty)
{
    if (QueueIsEmpty(obj))
    {
        *empty = 1;
        return 0;
    }
    int front = obj->data[obj->front++];
    //注意边界
    //模等一下置为有效范围
    obj->front %= obj->capacity;

    return front;

}
int main()
{
    int n = 0,q = 0;
    cirQueue obj;
    scanf("%d%d",&n,&q);
    QueueInit(&obj,n);
    while (q--)
    {
        int empty = 0;
        char s[6] = { 0 };
        scanf("%s",&s);
        if (strcmp(s,"push") == 0)
        {
            int x = 0;
            scanf("%d",&x);
            bool flag = QueuePush(&obj,x);
            if (!flag)
            {
                printf("full\n");
            }

        }
        else if (strcmp(s,"pop") == 0)
        {
            int front = QueuePop(&obj,&empty);
            if (empty == 1)
            {
                printf("empty\n");
            }
            else
            {
                printf("%d\n",front);
            }
        }
        else
        {
            int front = QueueFront(&obj,&empty);
            if (empty == 1)
            {
                 printf("empty\n");
            }
            else
            {
                printf("%d\n",front);
            }
        }
    }
    return 0;
}