数据结构与算法：栈和队列_元素进栈

三、栈和队列

（一）栈

1.栈：线性结构的一种特殊形式，元素满足先入后出

（1）元素依次入栈

（2）栈顶元素出栈

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2.元素入栈

（1）注意栈满

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3.元素出栈

（1）注意栈空

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4.代码实现

（1）顺序表实现

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

#define Elem int
typedef struct Stack {
	
	Elem* data;
	int capacity;
	int top;
	
}stack;

int init(stack* s,int capacity)
{
	int flag = 0;
	
	s->data = (Elem*)malloc(sizeof(Elem)*capacity);
	
	if(s->data == NULL)
		flag = -1;
	
	s->capacity = capacity;
	s->top = -1;
	
	return flag;
}

int IsEmpty(stack* s)
{
	int flag = 0;
	
	if(s->top == -1)
		flag = -1;
	
	return flag;
}

int IsFull(stack* s)
{
	int flag = 0;
	
	if(s->top == s->capacity - 1)
		flag = -1;
	
	return flag;
}

int push(stack* s,Elem data)
{
	int flag = 0;
	if(IsFull(s))
		flag = -1;
	else
		s->data[++s->top] = data;
	
	return flag;
	
}

int pop(stack* s)
{
	int flag = 0;
	
	if(IsEmpty(s))
		flag = -1;
	else
		s->top--;
	
	return flag;
	
}

void print(stack s)
{
	for(int i = 0;i <= s.top;i++)
		printf("%d ",s.data[i]);
}

int main()
{
   	/*  Write C code in this online editor and run it. */
	
	stack s;
	
	init(&s,5);
	
	for(int i = 0;i < 6;i++)
		push(&s,i);
	
	for(int i = 0;i < 4;i++)
		pop(&s);
	
	print(s);

   
   return 0;
}
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（2）链表实现

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

#define Elem int

typedef struct Linklist {
	
	Elem data;
	struct Linklist* next;
}linklist;

linklist* createNode(Elem data)
{
	linklist* node = (linklist*)malloc(sizeof(linklist));
	
	node->data = data;
	node->next = NULL;
	
	return node;
}

void push(linklist* head,Elem data)
{
	while(head->next)
		head = head->next;
	
	head->next = createNode(data);
}

void pop(linklist* *phead)
{
	linklist* temp = *phead;
	if(*phead)
	{
		*phead = (*phead)->next;
		free(temp);
	}
}

void print(linklist* head)
{
	while(head)
	{
		printf("%d ",head->data);
		head = head->next;
	}
}

int main()
{
   	/*  Write C code in this online editor and run it. */
	linklist* head;
	
	head = createNode(0);
	
	push(head,1);
	push(head,2);
	
	pop(&head);
	pop(&head);
	
	print(head);
	
	return 0;
}
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（二）队列

1.队列：线性结构的一种特殊形式，元素满足先入先出

（1）元素依次入队列

（2）队首元素出队列

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2.元素入队

（1）注意队满，对满时，rear + 1 = front

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3.元素出队

（1）注意队空，队空时，front = rear

（2）循环队列入队，rear = (rear + 1)%MAXSIZE

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4.代码实现

（1）顺序表实现队列（循环队列）

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

#define Elem int

typedef struct Queue {
	
	Elem* data;
	int capacity;
	int rear;
	int front;
	
}queue;

int init(queue* q,int capacity)
{
	int flag = 0;
	q->data = (Elem*)malloc(sizeof(Elem)*(capacity+1));
	
	if(q->data == NULL)
		flag = -1;
	
	q->capacity = capacity;
	q->rear = 0;
	q->front = 0;
}

int IsFull(const queue* q)
{
	int flag = 0;
	
	if((q->rear+1)%(q->capacity+1) == q->front)
		flag = -1;
	
	return flag;
}

int Enqueue(queue* q,Elem data)
{
	int flag = 0;
	if(IsFull(q))
		flag = -1;
	else
	{
		q->data[q->rear] = data;
		q->rear = (q->rear + 1)%(q->capacity+1);
	}
	
	return flag;
		
}

int IsEmpty(const queue* q)
{
	int flag = 0;
	
	if(q->front == q->rear)
		flag = -1;
	
	return flag;
}

int Dequeue(queue* q)
{
	int flag = 0;
	
	if(IsEmpty(q))
		flag = -1;
	else
		q->front = (q->front+1)%(q->capacity+1);
}

void print(queue q)
{
	int i = 0;
	for(i = q.front;i != q.rear;)
	{
		printf("%d ",q.data[i]);
		i = (i+1)%(q.capacity+1);
	}
}

int main()
{
   	/*  Write C code in this online editor and run it. */
 	queue q;
	
	init(&q,5);
	
	for(int i = 0;i < 6;i++)
		Enqueue(&q,i);

	Dequeue(&q);
	
	Enqueue(&q,5);
	

	print(q);
   
   	return 0;
}
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（2）链表实现队列

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

#define Elem int

typedef struct Linklist {
	
	Elem data;
	struct Linklist* next;
	
}linklist;

typedef struct Queue {
	
	linklist* front;
	linklist* rear;
	
}queue;

linklist* createNode(Elem data)
{
	linklist* node = (linklist*)malloc(sizeof(linklist));
	
	node->data = data;
	node->next = NULL;
	
	return node;
}

void init(queue* q)
{
	q->front = NULL;
	q->rear = NULL;
}

int Enqueue(queue* q,Elem data)
{
	int flag = 0;
	
	if(q->front == NULL)
	{
		q->front = createNode(data);
		if(q->front == NULL)
			flag = -1;
		q->rear = q->front;
	}
	else
	{
		q->rear->next = createNode(data);
		if(q->rear->next == NULL)
			flag = -1;
		q->rear = q->rear->next;
	}
	
	return flag;
}

int IsEmpty(const queue* q)
{
	int flag = 0;
	if(q->front == NULL)
		flag = -1;
	
	return flag;
}

int Dequeue(queue* q)
{
	int flag = 0;
	
	if(IsEmpty(q))
		flag = -1;
	else
	{
		linklist* temp = q->front;
		q->front = q->front->next;
		free(temp);
	}
	
	return flag;
	
	
}

void print(queue q)
{
	while(q.front)
	{
		printf("%d ",q.front->data);
		q.front = q.front->next;
	}
}

int main()
{
	/*  Write C code in this online editor and run it. */
	queue q;
	
	init(&q);
	
	int i = 0;
	for(i = 0;i < 5;i++)
		Enqueue(&q,i);
	
	
	for(i = 0;i < 3;i++)
		Dequeue(&q);
	
	Enqueue(&q,5);
	
	print(q);
   
   return 0;
}
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