c++ 字符串

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


#include <string>//模板类型
using std::string;
using std::endl;
using std::cout;


void test0(void)
{//栈空间
    char str1[] = "hello,world";
    char str2[] = "shengzhen";
    int len1 = sizeof(str1);
    int len2 = sizeof(str2);
    cout << "len1 = " << len1 << " , len2 = " << len2 << endl;

//    strcat(str1, str2);//第一个参数代表的数组空间一定要是足够的，否则在拼接字符串之后就会越界

    printf("%s\n", str1);
    printf("%s\n", str2);
    printf("%p\n", str1);
    printf("%p\n", str2);
}
void test1(void)
{//堆空间
    char *str1 = "hello,world";
    char *str2 = "shengzhen";
    int len = strlen(str1) + strlen(str2);
    char *ptr = (char *)malloc( len + 1);
    memset(ptr,0,len);

    int len1 = sizeof(str1);
    int len2 = sizeof(str2);
    cout << "len1 = " << len1 << " , len2 = " << len2 << endl;
    strcpy(ptr, str1);
    strcat(ptr, str2);//第一个参数代表的数组空间一定要是足够的，在拼接字符串之后不能越界
    char * p1 = strstr(str1, "world"); 
    
    char * p2 = (char *)malloc(strlen(p1) + 1);
    strcpy(p2, p1);
    printf("%s\n", p2);
    printf("%s\n", ptr);
    printf("%p\n", ptr);

    printf("%s\n", str1);
    printf("%s\n", str2);

    printf("%p\n", str1);
    printf("%p\n", str2);
    free(p2);
    free(ptr);
}


void test2()
{//c++ string 是一个类型
    string s1 = "hello,world";
    string s2 = "shengzhen";

    string s3 = s1 + s2;
    //可以把string看做一个数组来使用
    for (int idx = 0; idx < s1.size(); ++idx)
    {
        cout << s1[idx] <<" ; "<<idx << endl;
    }

    size_t pos = s1.find("world");//从头向尾查找
    string sub = s1.substr(pos, 5);

    //迭代器

    string::iterator it = s1.begin();
    for (; it != s1.end(); ++it)
    {
        cout << *it << endl;
    }

//    c++11
    for (auto & elem : s2)
    {//auto关键字可以进行类型的自动推到
        cout << elem << endl;
    }
    cout << "sub = " << sub<< endl;
    cout << "s1 = " << s1 << endl;
    cout << "s2 = " << s2 << endl;
    s3.append(" wangdao");
    cout << "s3 = " << s3 << endl;
    string s4= s1 + s2 + "lihui" + s3;
    cout << "s4 = "<<s4 << endl;
}
int main(void)
{
    test2();
    system("pause");
    return 0;
}