题解 | #【模板】循环队列#想抱抱他，又怕他生气

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

struct node {
    int* data;   // 动态分配的数组
    int front;
    int rear;
    int capacity;  // 队列的最大容量
};
typedef struct node* queue;

void push(queue ptrs, int item) {
    if ((ptrs->rear + 1) % ptrs->capacity == ptrs->front) {
        printf("full\n");  // 队列已满，无法入队
        return;
    }
    ptrs->rear = (ptrs->rear + 1) % ptrs->capacity;
    ptrs->data[ptrs->rear] = item;
}

int pop(queue ptrs) {
    if (ptrs->front == ptrs->rear) {
        printf("empty\n");  // 队列为空，无法出队
        return -1;
    }
    ptrs->front = (ptrs->front + 1) % ptrs->capacity;
    return ptrs->data[ptrs->front];
}

void front(queue ptrs) {
    if (ptrs->front == ptrs->rear) {
        printf("empty\n");  // 队列为空，无法获取头元素
        return;
    }
    printf("%d\n", ptrs->data[(ptrs->front + 1) % ptrs->capacity]);
}

int main() {
    queue ptrs = (queue)malloc(sizeof(struct node));

    int n, q;
    scanf("%d %d", &n, &q);

    ptrs->capacity = n + 1;  // 额外预留一个空间，因为循环队列中一个位置不存储数据
    ptrs->data = (int*)malloc(ptrs->capacity * sizeof(int));
    ptrs->front = 0;
    ptrs->rear = 0;

    char operation[10];
    int value;

    while (q--) {
        scanf("%s", operation);
        if (strcmp(operation, "push") == 0) {
            scanf("%d", &value);
            push(ptrs, value);
        } else if (strcmp(operation, "pop") == 0) {
            int result = pop(ptrs);
            if (result != -1) {
                printf("%d\n", result);
            }
        } else if (strcmp(operation, "front") == 0) {
            front(ptrs);
        }
    }

    free(ptrs->data);
    free(ptrs);
    return 0;
}