03队列及其操作

03队列及其操作

1、队列结构体

typedef struct Queue
{
    int *data;
    int head, tail, length, count;
} Queue;

 

2、队列初始化

Queue *init(int n)
{
    Queue *q = (Queue*)malloc(sizeof(Queue));
    q->data = (int*)malloc(sizeof(int) * n);
    q->head = q->tail = q->count = 0;
    q->length = n;
    
    return q;
}

 

3、获取当前队列头的位置

int front(Queue *q)
{
    return q->data[(q->head-1)%q->length];
}

 

4、判断队列是否为空

int empty(Queue *q)
{
    return q->count == 0;
}

 

5、入队操作

int push(Queue *q, int val)
{
    if (q == NULL) return 0;
    if (q->count == q->length) {
        if (!expand(q)) return 0;
        printf("expand success! Queue->size(%d)\n", q->length);
    }
    q->data[q->tail++] = val;
    if (q->tail == q->length) q->tail = 0;
    q->count += 1;
    
    return 1;
}

 

6、出队操作

int pop(Queue *q)
{
    if (q == NULL) return 0;
    if (empty(q)) return 0;
    q->head++;
    if (q->head == q->length) q->head = 0;
    q->count -= 1;
    
    return 1;
}

 

7、队列扩容

int expand(Queue *q)
{
    int extra_size = q->length;
    int *p;
    while (extra_size) {
        p = (int *)malloc(sizeof(int) * (q->length + extra_size));
        if (p) break;  // 扩容成功则退出 
        extra_size >> 2;  // 扩容不成功则大小缩小一倍再继续扩容 
    }
    if (p == NULL) return 0;
    // 扩容成功，将原队列的数据拷贝过来
    int i = q->head;
    int j;
    for (j=0;j<q->count;j++) {
        p[j] = q->data[(i+j) % q->length];  
    } 
    free(q->data);
    q->data = p;
    q->head = 0;
    q->tail = q->count;
    q->length += extra_size;
    
    return 1;
}

 

8、输出/打印队列元素

void output(Queue *q)
{
    printf("Queue : [");
    int i, j;
    for (i=q->head,j=0;j<q->count;i++,j++) {
        j && printf(", ");
        printf("%d", q->data[i % q->length]);
    }
    printf("]\n");
    
    return;
}

 

9、清除队列

void clear(Queue *q)
{
    if (q == NULL) return;
    free(q->data);
    free(q);
    
    return;
}

 

10、测试及整体代码

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

typedef struct Queue
{
    int *data;
    int head, tail, length, count;
} Queue;

Queue *init(int n)
{
    Queue *q = (Queue*)malloc(sizeof(Queue));
    q->data = (int*)malloc(sizeof(int) * n);
    q->head = q->tail = q->count = 0;
    q->length = n;
    
    return q;
}

int front(Queue *q)
{
    return q->data[(q->head-1)%q->length];
}

int empty(Queue *q)
{
    return q->count == 0;
}

int expand(Queue *q)
{
    int extra_size = q->length;
    int *p;
    while (extra_size) {
        p = (int *)malloc(sizeof(int) * (q->length + extra_size));
        if (p) break;  // 扩容成功则退出 
        extra_size >> 2;  // 扩容不成功则大小缩小一倍再继续扩容 
    }
    if (p == NULL) return 0;
    // 扩容成功，将原队列的数据拷贝过来
    int i = q->head;
    int j;
    for (j=0;j<q->count;j++) {
        p[j] = q->data[(i+j) % q->length];  
    } 
    free(q->data);
    q->data = p;
    q->head = 0;
    q->tail = q->count;
    q->length += extra_size;
    
    return 1;
}

int push(Queue *q, int val)
{
    if (q == NULL) return 0;
    if (q->count == q->length) {
        if (!expand(q)) return 0;
        printf("expand success! Queue->size(%d)\n", q->length);
    }
    q->data[q->tail++] = val;
    if (q->tail == q->length) q->tail = 0;
    q->count += 1;
    
    return 1;
}

int pop(Queue *q)
{
    if (q == NULL) return 0;
    if (empty(q)) return 0;
    q->head++;
    if (q->head == q->length) q->head = 0;
    q->count -= 1;
    
    return 1;
}

void output(Queue *q)
{
    printf("Queue : [");
    int i, j;
    for (i=q->head,j=0;j<q->count;i++,j++) {
        j && printf(", ");
        printf("%d", q->data[i % q->length]);
    }
    printf("]\n");
    
    return;
}

void clear(Queue *q)
{
    if (q == NULL) return;
    free(q->data);
    free(q);
    
    return;
}

int main()
{
    srand(time(0));
    #define max_op 20
    Queue *q = init(max_op);
    int i;
    for (i=0;i<max_op*2;i++) {
        int val = rand() % 100;
        int op = rand() % 4;
        switch(op) {
            case 0:
            case 1:
            case 2: {
                printf("push %d to Queue = %d\n", val, push(q, val));
                break;
            }
            case 3: {
                printf("pop %d from the Queue = %d\n", front(q), pop(q));
                break;
            }
        }
        output(q);
        printf("\n");
    }
    #undef max_op
    clear(q);
    
    return 0;
}

 

测试输出：