clist

c语言实现队列

栈的理解

队列(Queue)需要两个特征描述，队头（front）和队尾（rear），顾名思义，排队时后来者应跟在队尾，最前面的人应当最先出队

队列实现

数组实现

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX 3
int arr[MAX];
int front, rear;
bool isEmpty(){
	return (front == -1 && rear == -1) ? true : false;
}

bool isFull(){
	return (rear+1)%MAX == front ? true : false;
}

void enQueue(int x){
	if(isFull()){
		printf("queue is full\n");
	return;
}
if(isEmpty())
	front = rear = 0;
else
	rear = (rear+1)%MAX;
arr[rear] = x;
}
void deQueue(){
	if(isEmpty())
	{
		printf("queue is empty\n");
	return;
}
	else if(front == rear)
	front = rear = -1;
	else
	front = (front+1)%MAX;

}

void Print(){
	int length = (rear + MAX - front)%MAX + 1;
	int i;
	for( i = 0; i<length;i++)
	{
	printf("%d ", arr[(front+i)%MAX]);
	}
	printf("\n");
}

int main(){
	front = -1;
	rear = -1;
	enQueue(2); Print();
	enQueue(4); Print();
	enQueue(6); Print();
	deQueue(); Print();
	enQueue(10); Print();
	return 0;
}

链表实现(这是真没用）

#include<stdio.h>
#include<stdlib.h>
struct Node {
	int data;
	struct Node* next;
};
// Two glboal variables to store address of front and rear nodes. 
struct Node* front = NULL;
struct Node* rear = NULL;

// To Enqueue an integer
void Enqueue(int x) {
	struct Node* temp = 
		(struct Node*)malloc(sizeof(struct Node));
	temp->data =x; 
	temp->next = NULL;
	if(front == NULL && rear == NULL){
		front = rear = temp;
		return;
	}
	rear->next = temp;
	rear = temp;
}

// To Dequeue an integer.
void Dequeue() {
	struct Node* temp = front;
	if(front == NULL) {
		printf("Queue is Empty\n");
		return;
	}
	if(front == rear) {
		front = rear = NULL;
	}
	else {
		front = front->next;
	}
	free(temp);
}

int Front() {
	if(front == NULL) {
		printf("Queue is empty\n");
		return 0;
	}
	return front->data;
}

void Print() {
	struct Node* temp = front;
	while(temp != NULL) {
		printf("%d ",temp->data);
		temp = temp->next;
	}
	printf("\n");
}

int main(){
	/* Drive code to test the implementation. */
	// Printing elements in Queue after each Enqueue or Dequeue 
	Enqueue(2); Print(); 
	Enqueue(4); Print();
	Enqueue(6); Print();
	Dequeue();  Print();
	Enqueue(8); Print();
}