文章目录
- 写在前面
- 栈
- 什么是栈
- 栈的实现
- 队列
- 什么是队列
- 队列的实现
- 用队列实现栈
- 用栈模拟队列
写在前面
栈和队列的实现依托的是顺序表和链表,如果对顺序表和链表不清楚是很难真正理解栈和队列的
下面为顺序表和链表的实现和图解讲解
手撕图解顺序表
手撕图解单链表
栈
什么是栈
栈是一种数据结构,遵循的原则是后入先出,简单来说就是先入栈的最后出,最后入栈的先出
栈在实际应用中也是有很多场景,例如在使用网页时,我们点入了多个网页,退出返回的时候遵循的就是栈的后入先出原则
栈的实现
既然知道了栈的原则,那么就进行栈的实现用什么比较好,首先确定是可以用线性表实现,观察栈的使用原则不难发现,它只涉及一端的输入输出,这就意味着使用顺序表是很好的解决方案
栈的功能也不算多,入栈出栈检查栈满查看栈顶元素…整体看,栈就是顺序表的变形,这里对栈的实现不进行过多补充,重点在于后面和队列的相互实现
首先列出栈的定义和栈要实现的部分,声明和定义分离是个好习惯
// stack.h
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <stdbool.h>// 支持动态增长的栈
typedef int STDataType;
typedef struct Stack
{STDataType* _a;int _top; // 栈顶int _capacity; // 容量
}Stack;// 初始化栈
void StackInit(Stack* ps);// 入栈
void StackPush(Stack* ps, STDataType data);// 出栈
void StackPop(Stack* ps);// 获取栈顶元素
STDataType StackTop(Stack* ps);// 获取栈中有效元素个数
int StackSize(Stack* ps);// 检测栈是否为空,如果为空返回非零结果,如果不为空返回0
int StackEmpty(Stack* ps);// 销毁栈
void StackDestroy(Stack* ps);
下面是对栈的实现,几乎都是顺序表的基本操作,实现很简单
// stack.c
#include "stack.h"void StackInit(Stack* ps)
{assert(ps);STDataType* tmp = NULL;int newcapacity = ps->_capacity == 0 ? 4 : ps->_capacity * 2;tmp = (STDataType*)realloc(ps->_a, sizeof(STDataType) * newcapacity);if (tmp == NULL){perror("realloc fail");return;}ps->_capacity = newcapacity;ps->_a = tmp;
}void StackPush(Stack* ps, STDataType data)
{assert(ps);if (ps->_capacity == ps->_top){STDataType* tmp = NULL;int newcapacity = ps->_capacity == 0 ? 4:ps->_capacity * 2;tmp = (STDataType*)realloc(ps->_a,sizeof(STDataType)* newcapacity);if (tmp == NULL){perror("realloc fail");return;}ps->_capacity = newcapacity;ps->_a = tmp;}ps->_a[ps->_top] = data;ps->_top++;
}bool STEmpty(Stack* ps)
{assert(ps);return ps->_top == 0;
}void StackPop(Stack* ps)
{assert(ps);assert(!STEmpty(ps));ps->_top--;
}STDataType StackTop(Stack* ps)
{assert(ps);assert(!STEmpty(ps));return ps->_a[ps->_top-1];
}int StackSize(Stack* ps)
{assert(ps);return ps->_top;
}int StackEmpty(Stack* ps)
{assert(ps);if (0 == ps->_top)return 1;elsereturn 0;
}void StackDestroy(Stack* ps)
{assert(ps);ps->_capacity = 0;ps->_top = 0;free(ps->_a);ps->_a = NULL;
}
整体看,只要掌握了顺序表,栈的实现是很轻松的
队列
什么是队列
从名字来看,队列在日常生活中也经常遇到,不管在哪里都少不了排队的概念,而在有秩序的队列中,进队列都是从后面进队列,出队列都是从头出队列,这就类似于链表中的头删和尾插
那么队列的定义就有了,先进的先出,后进的后出,这就是队列的定义
队列实现还是和线性表有关,具体选顺序表还是链表要进行分析:
如果选用顺序表,顺序表的头删和尾插显然不如链表,你可能有这样的解决方案:我们可以选用数组下标当作头和尾,这样就能模拟头部少一个和尾部加一个,的确,这样可以解决,但是下一个问题是数组的长度并不好管控,如果想要完美的充分利用顺序表,就必须要使用循环数组,循环数组的下标并不好掌控,因此这里使用链表是很合适的选择
这里是关于循环数组的解析和模拟实现队列:
解析循环数组
队列的实现
// queue.h
#include<stdlib.h>
#include<assert.h>
#include<stdbool.h>typedef int QDataType;
typedef struct QueueNode
{struct QueueNode* next;QDataType data;
}QNode;typedef struct Queue
{QNode* phead;QNode* ptail;int size;
}Queue;void QueueInit(Queue* pq);void QueueDestroy(Queue* pq);void QueuePush(Queue* pq, QDataType x);void QueuePop(Queue* pq);QDataType QueueFront(Queue* pq);QDataType QueueBack(Queue* pq);int QueueSize(Queue* pq);bool QueueEmpty(Queue* pq);
上述函数的声明具体实现如下:
// queue.c
#include "queue.h"#include"Queue.h"void QueueInit(Queue* pq)
{assert(pq);pq->phead = NULL;pq->ptail = NULL;pq->size = 0;
}void QueueDestroy(Queue* pq)
{assert(pq);QNode* cur = pq->phead;while (cur){QNode* next = cur->next;free(cur);cur = next;}pq->phead = pq->ptail = NULL;pq->size = 0;
}void QueuePush(Queue* pq, QDataType x)
{assert(pq);QNode* newnode = (QNode*)malloc(sizeof(QNode));if (newnode == NULL){perror("malloc fail\n");return;}newnode->data = x;newnode->next = NULL;if (pq->ptail == NULL){assert(pq->phead == NULL);pq->phead = pq->ptail = newnode;}else{pq->ptail->next = newnode;pq->ptail = newnode;}pq->size++;
}void QueuePop(Queue* pq)
{assert(pq);assert(!QueueEmpty(pq));// 1、一个节点// 2、多个节点if (pq->phead->next == NULL){free(pq->phead);pq->phead = pq->ptail = NULL;}else{// 头删QNode* next = pq->phead->next;free(pq->phead);pq->phead = next;}pq->size--;
}QDataType QueueFront(Queue* pq)
{assert(pq);assert(!QueueEmpty(pq));return pq->phead->data;
}QDataType QueueBack(Queue* pq)
{assert(pq);assert(!QueueEmpty(pq));return pq->ptail->data;
}int QueueSize(Queue* pq)
{assert(pq);return pq->size;
}bool QueueEmpty(Queue* pq)
{assert(pq);return pq->size == 0;
}
栈和队列本身是没有难度的,但是如果使用栈去实现队列,用队列去实现栈呢?
下面分析如何实现队列和栈的相互实现:
用队列实现栈
先看原理图:
代码实现也不算难,实现如下:
#include<stdlib.h>
#include<assert.h>
#include<stdbool.h>typedef int QDataType;
typedef struct QueueNode
{struct QueueNode* next;QDataType data;
}QNode;typedef struct Queue
{QNode* phead;QNode* ptail;int size;
}Queue;
#include "queue.h"#include"Queue.h"void QueueInit(Queue* pq)
{assert(pq);pq->phead = NULL;pq->ptail = NULL;pq->size = 0;
}void QueueDestroy(Queue* pq)
{assert(pq);QNode* cur = pq->phead;while (cur){QNode* next = cur->next;free(cur);cur = next;}pq->phead = pq->ptail = NULL;pq->size = 0;
}void QueuePush(Queue* pq, QDataType x)
{assert(pq);QNode* newnode = (QNode*)malloc(sizeof(QNode));if (newnode == NULL){perror("malloc fail\n");return;}newnode->data = x;newnode->next = NULL;if (pq->ptail == NULL){assert(pq->phead == NULL);pq->phead = pq->ptail = newnode;}else{pq->ptail->next = newnode;pq->ptail = newnode;}pq->size++;
}void QueuePop(Queue* pq)
{assert(pq);assert(!QueueEmpty(pq));// 1、一个节点// 2、多个节点if (pq->phead->next == NULL){free(pq->phead);pq->phead = pq->ptail = NULL;}else{// 头删QNode* next = pq->phead->next;free(pq->phead);pq->phead = next;}pq->size--;
}QDataType QueueFront(Queue* pq)
{assert(pq);assert(!QueueEmpty(pq));return pq->phead->data;
}QDataType QueueBack(Queue* pq)
{assert(pq);assert(!QueueEmpty(pq));return pq->ptail->data;
}int QueueSize(Queue* pq)
{assert(pq);return pq->size;
}bool QueueEmpty(Queue* pq)
{assert(pq);return pq->size == 0;
}
typedef struct Mystack
{Queue push;Queue pop;
}Mystack;void MsInit(Mystack* ps)
{assert(ps);QueueInit(&(ps->push));QueueInit(&(ps->pop));
}void MsPush(Mystack* ps,QDataType x)
{assert(ps);QueuePush(&(ps->push), x);
}void MsPop(Mystack* ps)
{while (QueueSize(&(ps->push)) > 1){QueuePush(&(ps->pop), QueueFront(&(ps->push)));QueuePop(&(ps->push));}QueuePop(&(ps->push));while (!QueueEmpty(&(ps->pop))){QueuePush(&(ps->push), QueueFront(&(ps->pop)));QueuePop(&(ps->pop));}
}QDataType MsTop(Mystack* ps)
{assert(ps);return ps->push.ptail->data;
}bool MsEmpty(Mystack* ps)
{if (ps->push.size == 0)return true;return false;
}int main()
{Mystack s;MsInit(&s);MsPush(&s, 1);MsPush(&s, 2);MsPush(&s, 3);MsPush(&s, 4);MsPush(&s, 5);while (!MsEmpty(&s)){printf("%d ", MsTop(&s));MsPop(&s);}return 0;
}
用栈模拟队列
和上面的比起来,栈来实现队列就有一些改变:
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <stdbool.h>// 支持动态增长的栈
typedef int STDataType;
typedef struct Stack
{STDataType* _a;int _top; // 栈顶int _capacity; // 容量
}Stack;void StackInit(Stack* ps)
{assert(ps);ps->_a = NULL;ps->_top = 0;ps->_capacity = 0;
}void StackPush(Stack* ps, STDataType data)
{assert(ps);if (ps->_capacity == ps->_top){STDataType* tmp = NULL;int newcapacity = ps->_capacity == 0 ? 4:ps->_capacity * 2;tmp = (STDataType*)realloc(ps->_a,sizeof(STDataType)* newcapacity);if (tmp == NULL){perror("realloc fail");return;}ps->_capacity = newcapacity;ps->_a = tmp;}ps->_a[ps->_top] = data;ps->_top++;
}bool STEmpty(Stack* ps)
{assert(ps);return ps->_top == 0;
}void StackPop(Stack* ps)
{assert(ps);assert(!STEmpty(ps));ps->_top--;
}STDataType StackTop(Stack* ps)
{assert(ps);assert(!STEmpty(ps));return ps->_a[ps->_top-1];
}int StackSize(Stack* ps)
{assert(ps);return ps->_top;
}int StackEmpty(Stack* ps)
{assert(ps);if (0 == ps->_top)return 1;elsereturn 0;
}void StackDestroy(Stack* ps)
{assert(ps);ps->_capacity = 0;ps->_top = 0;free(ps->_a);ps->_a = NULL;
}
typedef struct Myqueue
{Stack Push;Stack Pop;
}Myqueue;void MqInit(Myqueue* pq)
{assert(pq);StackInit(&(pq->Push));StackInit(&(pq->Pop));
}void MqPush(Myqueue* pq,STDataType x)
{assert(pq);StackPush(&(pq->Push), x);
}void MqPop(Myqueue* pq)
{while (!StackEmpty(&(pq->Push))){StackPush(&(pq->Pop), StackTop(&(pq->Push)));StackPop(&(pq->Push));}StackPop(&(pq->Pop));while (!StackEmpty(&(pq->Pop))){StackPush(&(pq->Push), StackTop(&(pq->Pop)));StackPop(&(pq->Pop));}
}STDataType MqTop(Myqueue* pq)
{// 把数据从push弄到popwhile (!StackEmpty(&(pq->Push))){StackPush(&(pq->Pop), StackTop(&(pq->Push)));StackPop(&(pq->Push));}STDataType ret = pq->Pop._a[pq->Pop._top-1];// 再把数据弄回去while (!StackEmpty(&(pq->Pop))){StackPush(&(pq->Push), StackTop(&(pq->Pop)));StackPop(&(pq->Pop));}return ret;
}int MqEmpty(Myqueue* pq)
{if (pq->Push._top == 0)return 1;return 0;
}int main()
{Myqueue q;MqInit(&q);MqPush(&q, 1);MqPush(&q, 2);MqPush(&q, 3);MqPush(&q, 4);MqPush(&q, 5);while (!MqEmpty(&q)){printf("%d ", MqTop(&q));MqPop(&q);}return 0;
}
这样就可以直接实现了
整体来说,栈和队列的相互实现的意义不算很大,但是可以很好的更加深入的理解栈和队列的原理