博客

1.引用头文件

2.函数重载

• C++支持函数重载

//#include <iostream>
#include <cstdio>
using namespace std;
void printf(){
        printf("Hello World!\n");
}
int main(){
        printf();
}

3.命名空间

• C++支持命名空间：避免全局变量、函数、类的命名冲突（因名字相同而编译失败）

namespace 空间名{
	定义类//函数
}

using namespace 空间名;

using std::cout; //using 空间名::标识符;

#include <iostream>
#include <cstdio>
using namespace std;
namespace salt{
        void printf(){
                cout << "Hello Salt" << endl;
        }
}
namespace sugar{
        void printf(){
                cout << "Hello Sugar" << endl;
        }
}
using namespace sugar;
int main(){
        //salt::printf();
        //sugar::printf();
        printf();
}

4.类型

• bool:true – false 内置类型和常量。

5.动态内存

*p = new void; //申请void型的动态内存
delete p;      //释放内存

int* p = new int[n];
delete [] p;

#include <iostream>
#include <cstdlib>
#include <cstdio>
using namespace std;
int main(){
        //C
        int* p = (int*)malloc(sizeof(int));
        *p = 100;
        printf("%p %d\n",p,*p);

        //C++
        int* q = new int;
        *q = 200;
        cout << q << " " << *q << endl;

        //C
        free(p);
        p = NULL;
        	
        //C++   
        delete q;
        q = NULL;
        	
		//C
        int n;
        scanf("%d",&n);
        int* arr = (int*)malloc(sizeof(int)*n);
        for (int i=0;i<n;i++){
                scanf("%d",arr+i);
        }
        for (int i=0;i<n;i++){
                printf("%d\n",arr[i]);
        }
        free(arr);
        arr = NULL;
        	
		//C++
        {
        int n;
        cin >> n;
        int* parr = new int[n];
        for (int i=0;i<n;i++){
                cin >> parr[i];
        }
        for (int i=0;i<n;i++){
                cout << parr[i] << endl;
        }
        delete [] parr;
        parr = NULL;
        }
        
		//C
        {
        int n;
        scanf("%d",&n);
        getchar();
        char* arr = (char*)malloc(sizeof(int)*(n+1));
        for (int i=0;i<n;i++){
                scanf("%c",arr+i);
        }
        arr[n] = '\0';
        for (int i=0;i<n;i++){
                printf("%c\n",arr[i]);
        }
        free(arr);
        arr = NULL;
        }
        
		//C++
        {
        int n;
        cin >> n;
        char* parr = new char[n];
        /*
        for (int i=0;i<n;i++){
                cin >> parr[i];
        }
        */
        cin >> parr;
        parr[n] = '\0';
        cout << parr << endl;
        /*      
        for (int i=0;i<n;i++){
                cout << parr[i] << endl;
        }
        */
        delete [] parr;
        parr = NULL;
        }
}

• realloc

int* temp = new int[size];
for (int i=0;i<n;i++){
	temp[i] = data[i];
}
// 可用memcpy()
// memcpy(temp,data,sizeof(Elemeent)*size)
delete [] data;
data = temp;

• 栈 -顺序表

#include <iostream>
// 栈 - 顺序表 // 倒序输出
using namespace std;
typedef int Element;
class Stack{
        Element* data;
        size_t size;
public:
        // 初始化
        void Create(){
                data = NULL;
                size = 0;
        }
        void Destory(){
                delete [] data;
                data = NULL;
                size = 0;
        }
        size_t GetSize(){
                return size;
        }
        // 入栈
        bool Push(int e){
                // realloc();
                Element* temp = new Element[size+1];
                if(NULL == temp) return false; // 没有申请到内存
                // 将data[]中的数复制到temp中
                for (int i=0;i<size;i++){
                        temp[i] = data[i];
                }
                delete [] data; // 释放data;
                data = temp; // 重新将temp赋值给data
                data[size] = e; // 数组长度size+1 data[size] 为数组最后一个元素
                size++;
                return true;
        }
        // 出栈
        bool Pop(){
                if(NULL == data) return false; // 空栈不出栈
                --size; // 栈长度减一

                Element* temp = new Element[size];
                if(NULL == temp) return false;
                for (int i=0;i<size;i++){
                        temp[i] = data[i];
                }
                delete [] data;
                data = temp;
                return true;
        }
        // 获得栈顶元素
        Element* GetTop(){
                return &data[size-1];
        }
};
int main(){
        Stack s;
        s.Create(); // 初始化栈
        for (;;){
                int e;
                if(!(cin >> e)) break;
                s.Push(e);
        }
        while (0 != s.GetSize()){
                cout << *s.GetTop() << endl;
                s.Pop();
        }
        s.Destory();
}

6.初始化

int n(num);

#include <iostream>
using namespace std;
int main(){
        //C
        int n = 10;
        float f = 1.1;
        printf("%d\n%f\n",n,f);
        int arr[3] = {1,2,3};
        for (int i=0;i<3;i++){
                printf("%d\n",arr[i]);
        }
        int* p = (int*)malloc(sizeof(int)); // 防止野指针
        *p = 10;
        printf("%d\n",*p);
        char c = 'a';
        printf("%c\n",c);
        char* s = (char*)"abc";
        printf("%s\n",s);
        
        //C++
        {
        int n(20);
        float f(2.2);
        cout << n << endl << f << endl;
        int arr[3] = {3,4,5};
        for (int i=0;i<3;i++){
                cout << arr[i] << " ";
        }
        cout << endl;
        int* p = new int; // 防止野指针
        *p = 200;;
        cout << *p << endl;
        char c('z');
        cout << c << endl;
        char* s((char*)"def");
        cout << s << endl;
        }
}