C++与C语言常用的语法对比

#include <iostream>
#include <ctime>
#include <stdlib.h>
#include <random>

#include <time.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/msg.h>
#include <sys/ipc.h>
#include <sys/wait.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdbool.h>
#include <malloc.h>

struct Hello{
	void sayHello(char *name){
		printf("你好，%s\n",name);
	}
};

int main()
{
	Hello hello;
	hello.sayHello();
	exit(0);
}

struct Hello{
	void (*sayHello)(char* name);   //函数名为指针类型
};
void sayHello(char* name){
	printf("你好，%s\n",name);
}
int main(){
	struct Hello hello;  //声明结构体的变量，需要加struct
	hello.sayHello=sayHello;  //C语言需要使用函数指针指向函数的声明！！！
	hello.sayHello("浅若清风");
	return 0;
}

void f()
{
	int n;
	int m;
	int *Array1;  //声明一维动态数组
	Array1=new int(n);  //为一维动态数组分配空间，元素个数为n
	int **Array2;  //声明二维动态数组
	Array2=new int*[n];  //为二维动态数组分配空间（n个指针空间），n行
	for(int i;i<n;++i)
	{
		Array2[i]=new int[m];  //为每一行分配内存空间（m个整数空间），m列
	}
	//释放内存
	delete []Array1;
	for(int i=0;i<n;++i){
		delete[]Array2[i];
	}
	delete[]Array2;
}

void f()
{
	int n;
	int m;
	int *Array1;  //声明一维动态数组
	Array1=(int *)calloc(n,sizeof(int));  //为一维动态数组分配空间，元素个数为n
	int **Array2;  //声明二维动态数组
	Array2=(int **)calloc(n,sizeof(int*));  //为二维动态数组分配空间（n个指针空间），n行
	for(int i;i<n;++i)
	{
		Array2[i]=(int*)calloc(m,sizeof(int));  //为每一行分配内存空间（m个整数空间），m列
	}
	//释放内存
	free(Array1);
	for(int i=0;i<n;++i){
		free(Array2[i]);
	}
	free(Array2);
}

#include<iostream>
using namespace std;

class QueueNode  //队列结点
{
public:
	QueueNode() :page(-1), next(NULL) {};
	QueueNode(int m_page, QueueNode* m_next = NULL) :page(m_page), next(m_next) {};
	~QueueNode() { next = NULL; }
public:
	int page;
	QueueNode* next;  //储存下一个结点的指针
};

class LinkQueue  //队列
{
public:
	LinkQueue() { front = rear = new QueueNode(); count = 0; }
	void push(int m_page);  //加到队尾
	int pop();  //取出队首结点（此例是包含头指针的链队，头指针的下一个结点才是队首结点），并返回该结点值
	bool exist(int page);  //判断队列中是否有结点的值为page
	void print(int page);  //打印队列

	QueueNode* front;  //队首指针
	QueueNode* rear;  //队尾指针
	int count;  //统计结点数量
};

void LinkQueue::push(int m_page)
{
	QueueNode* p = new QueueNode(m_page);
	p->next = NULL;
	rear->next = p;
	rear = p;
	count++;
}

int LinkQueue::pop()
{
	if (front == rear) {
		printf("队列为空！\n");
		return 0;
	}
	int top = front->next->page;  //记录队首，作为返回值
	QueueNode* tmp = front->next;
	front->next = tmp->next;
	if (rear == tmp)  //只剩下一个元素，此题不会出现这种情况
	{
		rear = front;
	}
	delete tmp;
	count--;
	return top;
}

void LinkQueue::print()  //打印队列
{
	QueueNode* p = front;
	while (p->next != NULL)
	{
			printf("%d ", p->next->page);
			p = p->next;
	}
	printf("\n");
}

bool LinkQueue::exist(int page) {  //判断队列中是否存在元素page
	QueueNode*p = front;
	while (p->next != NULL) {
		if (p->next->page == page) {
			return true;
		}
		else {
			p = p->next;
		}
	}
	return false;
}

int main()
{
	LinkQueue queue;
	for(int i=0;i<5;++i)
	{
		queue.push(i);
	}
	queue.print();
	if(queue.exit(6)) printf("yes!\n");
	else printf("no!\n");
	int top=queue.pop();  //获得队首元素值
	printf("队首元素的值为%d\n",top);
}

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

struct QueueNode
{
	int page;
	struct QueueNode *next;
};

typedef struct LinkQueue {
	struct QueueNode* front;
	struct QueueNode* rear;
	int count;
};

void initQueue(struct LinkQueue *q)
{
	q->front = q->rear=(struct QueueNode *)malloc(sizeof(struct QueueNode));
	q->front->next = NULL;
	q->count=0;
}

void push(struct LinkQueue *q, int page)
{
	struct QueueNode* node = (struct QueueNode*)malloc(sizeof(struct QueueNode));
	node->next = NULL;
	node->page = page;
	q->rear->next = node;  //与新增结点链接
	q->rear=node;  //尾指针后移
	q->count++;
}

int pop(struct LinkQueue*q)  //队首元素出队，并返回数值
{
	int top = q->front->next->page;
	struct QueueNode *node = q->front->next;
	q->front->next = q->front->next->next;
	free(node);
	return top;
}

bool exist(struct LinkQueue*q, int page)  //判断队列是否有结点的值等于page
{
	struct QueueNode *node = q->front;
	while (node->next != NULL)
	{
		if (node->next->page == page) return true;
		else node = node->next;
	}
	return false;
}

void print(struct LinkQueue *q)
{	
	struct QueueNode *node =q->front;
	while (node->next != NULL)
	{
		printf("%d ", node->next->page);
		node = node->next;
	}
	printf("\n");
}

int main()
{
	struct LinkQueue queue;
	initQueue(&queue);
	for (int i = 1; i < 5; ++i)
	{
		push(&queue, i);
	}
	print(&queue);
	if (exist(&queue, 3)) printf("yes!\n");
	printf("======\n");
	if (exist(&queue, 6)) printf("yes!\n");
	else printf("no!\n");
	int top = pop(&queue);
	printf("队首元素的值为%d\n", top);
}