栈和队列相关|有效的括号|用队列实现栈|用栈实现队列|设计循环队列(C)

于 2024-10-30 22:41:37 发布
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分类专栏： 数据结构OJ 文章标签： c语言 linux 开发语言
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本文链接：https://blog.youkuaiyun.com/CoderZzz6310/article/details/143376509
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20. 有效的括号

判断左右括号是否匹配，匹配返回true，不匹配返回false
通过栈来实现，类型和顺序，数量都要匹配
控制数量通过size
每个右括号都要找最近的左括号去判断类型匹配不匹配，顺序匹配不匹配
最后来判断数量匹配不匹配

  1. 左括号，入栈
  2. 右括号，出栈顶括号，进行匹配
栈接口
#include<stdio.h>
#include<stdlib.h>
#include<assert.h>
#include<stdbool.h>

typedef char STDataType;
typedef struct Stack
{
	STDataType* a;
	int top;
	int capacity;
}ST;

void STInit(ST* ps)
{
	assert(ps);
	ps->a = NULL;
	ps->capacity = 0;
	ps->top = 0;
}

void STDestroy(ST* ps)
{
	assert(ps);

	free(ps->a);
	ps->a = NULL;
	ps->top = ps->capacity = 0;
}

void STPush(ST* ps, STDataType x)
{
	assert(ps);
	// 11:40
	if (ps->top == ps->capacity)
	{
		int newCapacity = ps->capacity == 0 ? 4 : ps->capacity * 2;
		STDataType* tmp = (STDataType*)realloc(ps->a, sizeof(STDataType) * newCapacity);
		if (tmp == NULL)
		{
			perror("realloc fail");
			exit(-1);
		}

		ps->a = tmp;
		ps->capacity = newCapacity;
	}

	ps->a[ps->top] = x;
	ps->top++;
}

void STPop(ST* ps)
{
	assert(ps);

	// 
	assert(ps->top > 0);

	--ps->top;
}

STDataType STTop(ST* ps)
{
	assert(ps);

	// 
	assert(ps->top > 0);

	return ps->a[ps->top - 1];
}

int STSize(ST* ps)
{
	assert(ps);

	return ps->top;
}

bool STEmpty(ST* ps)
{
	assert(ps);

	return ps->top == 0;
}
if版本

bool isValid(char * s){
    ST st;
    STInit(&st);
    char top;
    while(*s)
    {
        if (*s == '[' || *s == '(' || *s == '{')
        {
            STPush(&st, *s);
        }
        else
        {
	        //数量不匹配
            if (STEmpty(&st))
            {
                STDestroy(&st);
                return false;
            }
            top = STTop(&st);
            STPop(&st);
            //顺序不匹配
            if((*s == ']' && top != '[')
            || (*s == ')' && top != '(')
            || (*s == '}' && top != '{'))
            {
                STDestroy(&st);
                return false;
            }
        }
        ++s;
    }

	// 栈不为空，false，说明数量不匹配
    bool ret = STEmpty(&st);
    STDestroy(&st);
    return ret;
}
switch版本
bool isValid(char * s){
    ST st;
    STInit(&st);
    char top;
  
    while (*s)
    {
        switch(*s)
        {
            case '[':
            case '(':
            case '{':
                STPush(&st, *s);
                break;
            case '}':
                // 数量不匹配
                if (STEmpty(&st))
                    return false;
  
                top = STTop(&st);
                STPop(&st);
                // 顺序不匹配
                if (top != '{')
                    return false;
                break;
            case ']':
                // 数量不匹配
                if (STEmpty(&st))
                    return false;
  
                top = STTop(&st);
                STPop(&st);
                //顺序不匹配
                if (top != '[')
                    return false;
                break;
            case ')':
                // 数量不匹配
                if (STEmpty(&st))
                    return false;
  
                top = STTop(&st);
                STPop(&st);
                //顺序不匹配
                if (top != '(')
                    return false;
                break;
        }
  
        ++s;
    }
  
    //数量不匹配
    bool ret = STEmpty(&st);
    STDestroy(&st);
    return ret;
}

225. 用队列实现栈

用两个队列实现栈

Push 1 2 3 4
![[Pasted image 20241030145528.png]]

Pop 4
分别出1 2 3，插入到另一个队列，最后剩下4，把最后一个数据Pop掉
![[Pasted image 20241030150220.png]]

![[Pasted image 20241030150525.png]]

Push 5 6
入到不为空的那个队列里
![[Pasted image 20241030150637.png]]

空队列是用来倒数据的

Pop 6
![[Pasted image 20241030151026.png]]

入队列：不为空的队列
出队列：不为空队列前N-1个出队列，插入空队列；删除剩余数据

队列接口
typedef int QDataType;
typedef struct QueueNode
{
	struct QueueNode* next;
	QDataType data;
}QNode;

typedef struct Queue
{
	QNode* head;
	QNode* tail;
	int size;
}Que;

void QueueInit(Que* pq);
void QueueDestroy(Que* pq);
void QueuePush(Que* pq, QDataType x);
void QueuePop(Que* pq);
QDataType QueueFront(Que* pq);
QDataType QueueBack(Que* pq);
bool QueueEmpty(Que* pq);
int QueueSize(Que* pq);

void QueueInit(Que* pq)
{
	assert(pq);

	pq->head = pq->tail = NULL;
	pq->size = 0;
}

void QueueDestroy(Que* pq)
{
	assert(pq);

	QNode* cur = pq->head;
	while (cur)
	{
		QNode* next = cur->next;
		free(cur);
		cur = next;
	}

	pq->head = pq->tail = NULL;
	pq->size = 0;
}

void QueuePush(Que* pq, QDataType x)
{
	assert(pq);

	QNode* newnode = (QNode*)malloc(sizeof(QNode));
	if (newnode == NULL)
	{
		perror("malloc fail");
		exit(-1);
	}

	newnode->data = x;
	newnode->next = NULL;

	if (pq->tail == NULL)
	{
		pq->head = pq->tail = newnode;
	}
	else
	{
		pq->tail->next = newnode;
		pq->tail = newnode;
	}

	pq->size++;
}

void QueuePop(Que* pq)
{
	assert(pq);
	assert(!QueueEmpty(pq));

	if (pq->head->next == NULL)
	{
		free(pq->head);
		pq->head = pq->tail = NULL;
	}
	else
	{
		QNode* next = pq->head->next;
		free(pq->head);
		pq->head = next;
	}

	pq->size--;
}

QDataType QueueFront(Que* pq)
{
	assert(pq);
	assert(!QueueEmpty(pq));

	return pq->head->data;
}

QDataType QueueBack(Que* pq)
{
	assert(pq);
	assert(!QueueEmpty(pq));

	return pq->tail->data;
}

bool QueueEmpty(Que* pq)
{
	assert(pq);

	return pq->head == NULL;
}

int QueueSize(Que* pq)
{
	assert(pq);

	return pq->size;
}
队列实现栈

![[Pasted image 20241030160553.png]]

typedef struct {
    Que q1;
    Que q2;
} MyStack;


MyStack* myStackCreate() {
    MyStack* pst = (MyStack*)malloc(sizeof(MyStack));
    QueueInit(&pst->q1);
    QueueInit(&pst->q2);

    return pst;
}

void myStackPush(MyStack* obj, int x) {
    if (!QueueEmpty(&obj->q1))
    {
        QueuePush(&obj->q1, x);
    }
    else
    {
        QueuePush(&obj->q2, x);
    }
}

int myStackPop(MyStack* obj) {
    Que* empty = &obj->q1;
    Que* nonempty = &obj->q2;
    if (!QueueEmpty(&obj->q1))
    {
        nonempty = &obj->q1;
        empty = &obj->q2;
    }

    while(QueueSize(nonempty) > 1)
    {
	    // 前size-1个导入空队列
        QueuePush(empty, QueueFront(nonempty));
        QueuePop(nonempty);
    }

    int top = QueueFront(nonempty);
    QueuePop(nonempty);
    return top;
}

int myStackTop(MyStack* obj) {
    if (!QueueEmpty(&obj->q1))
    {
        return QueueBack(&obj->q1);
    }
    else
    {
        return QueueBack(&obj->q2);
    }
}

bool myStackEmpty(MyStack* obj) {
    return QueueEmpty(&obj->q1) && QueueEmpty(&obj->q2);
}

void myStackFree(MyStack* obj) {
    QueueDestroy(&obj->q1);
    QueueDestroy(&obj->q2);

    free(obj);
}

232. 用栈实现队列

用两个栈来实现队列
Push 1 2 3 4
![[Pasted image 20241030185925.png]]

Pop 1
把数据往另一个栈里倒
![[Pasted image 20241030190053.png]]

Push 5 6
![[Pasted image 20241030190441.png]]

存数据的栈称为pushst，出数据的栈称为popst

栈接口
typedef int STDataType;
typedef struct Stack
{
	STDataType* a;
	int top;
	int capacity;
}ST;

void STInit(ST* ps)
{
	assert(ps);
	ps->a = NULL;
	ps->capacity = 0;
	ps->top = 0;
}

void STDestroy(ST* ps)
{
	assert(ps);

	free(ps->a);
	ps->a = NULL;
	ps->top = ps->capacity = 0;
}

void STPush(ST* ps, STDataType x)
{
	assert(ps);
	// 11:40
	if (ps->top == ps->capacity)
	{
		int newCapacity = ps->capacity == 0 ? 4 : ps->capacity * 2;
		STDataType* tmp = (STDataType*)realloc(ps->a, sizeof(STDataType) * newCapacity);
		if (tmp == NULL)
		{
			perror("realloc fail");
			exit(-1);
		}

		ps->a = tmp;
		ps->capacity = newCapacity;
	}

	ps->a[ps->top] = x;
	ps->top++;
}

void STPop(ST* ps)
{
	assert(ps);

	// 
	assert(ps->top > 0);

	--ps->top;
}

STDataType STTop(ST* ps)
{
	assert(ps);

	// 
	assert(ps->top > 0);

	return ps->a[ps->top - 1];
}

int STSize(ST* ps)
{
	assert(ps);

	return ps->top;
}

bool STEmpty(ST* ps)
{
	assert(ps);

	return ps->top == 0;
}
栈实现队列

typedef struct {
    ST pushst;
    ST popst;
} MyQueue;


MyQueue* myQueueCreate() {
    MyQueue* obj = (MyQueue*)malloc(sizeof(MyQueue));
    STInit(&obj->pushst);
    STInit(&obj->popst);

    return obj;
}

void myQueuePush(MyQueue* obj, int x) {
    STPush(&obj->pushst, x);
}

int myQueuePeek(MyQueue* obj) {
    if(STEmpty(&obj->popst))
    {
	    // 倒数据
        while(!STEmpty(&obj->pushst))
        {
            STPush(&obj->popst, STTop(&obj->pushst));
            STPop(&obj->pushst);
        }
    }
    return STTop(&obj->popst);
}

int myQueuePop(MyQueue* obj) {
    int front = myQueuePeek(obj);
    STPop(&obj->popst);
    return front;
}

bool myQueueEmpty(MyQueue* obj) {
    return STEmpty(&obj->popst) && STEmpty(&obj->pushst);
}

void myQueueFree(MyQueue* obj) {
    STDestroy(&obj->popst);
    STDestroy(&obj->pushst);

    free(obj);
}

622. 设计循环队列

![[Pasted image 20241030200421.png]]

循环队列
Pop 1
![[Pasted image 20241030200445.png]]

Push 5
在这里插入图片描述

Pop 2
![[Pasted image 20241030200620.png]]

Push 6
![[Pasted image 20241030200639.png]]

当队列为空
![[Pasted image 20241030200914.png]]

front和rear相等，队列为空
插入一个数据，rear往后走
rear不是指向最后一个数据，而是指向最后一个数据的下一个位置

如何判断队列满

多开一个空间
k == 4，表示队列只能存四个数
![[Pasted image 20241030202645.png]]

front == rear 空
rear的下一个就是front 满

  • rear在中间的情况
    ![[Pasted image 20241030205436.png]]
(rear + 1)% (k + 1) == front
取队尾

![[Pasted image 20241030212834.png]]

![[Pasted image 20241030212743.png]]

(rear + (k + 1) - 1) % (k + 1)

循环队列实现
typedef struct {
    int* a;
    int front;
    int rear;
    int k;
} MyCircularQueue;

MyCircularQueue* myCircularQueueCreate(int k) {
    MyCircularQueue* obj = (MyCircularQueue*)malloc(sizeof(MyCircularQueue));
    // 多开一个方便区分空和满
    obj->a = (int*)malloc(sizeof(int)*(k+1));
    obj->front = obj->rear = 0;
    obj->k = k;

    return obj;
}

bool myCircularQueueIsEmpty(MyCircularQueue* obj) {
    return obj->front == obj->rear;
}

bool myCircularQueueIsFull(MyCircularQueue* obj) {
    return (obj->rear + 1)%(obj->k + 1) == obj->front;
}

bool myCircularQueueEnQueue(MyCircularQueue* obj, int value) {
    if(myCircularQueueIsFull(obj))
        return false;
    
    obj->a[obj->rear] = value;
    obj->rear++;

    obj->rear %= (obj->k + 1);

    return true;
}

bool myCircularQueueDeQueue(MyCircularQueue* obj) {
    if (myCircularQueueIsEmpty(obj))
        return false;
    
    ++obj->front;
    obj->front %= (obj->k + 1);
    return true;
}

int myCircularQueueFront(MyCircularQueue* obj) {
    if (myCircularQueueIsEmpty(obj))
        return -1;
    else
        return obj->a[obj->front];
}

int myCircularQueueRear(MyCircularQueue* obj) {
    if (myCircularQueueIsEmpty(obj))
        return -1;
    else
	    //(rear + (k + 1) - 1) % (k + 1)
        return obj->a[(obj->rear + obj->k) % (obj->k + 1)];
}

void myCircularQueueFree(MyCircularQueue* obj) {
    free(obj->a);
    free(obj);
}
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