C++中string的操作

int main()
{
    string s1="aaa";
    string s2="bbb";
    string s3=s1;   //考虑构造函数
    string s4(10,‘a‘);  //初始化为“aaaaaaaaaa"
    cout<<s1<<endl;
    cout<<s2<<endl;
    cout<<s3<<endl;
    cout<<s4<<endl;

    cout<<"迭代器方法"<<endl;
    for( string::iterator it = s1.begin(); it != s1.end(); it++ ){
        cout<< *it <<" ";
    }
    cout<<"\nat方法取元素"<<endl;
    //使用at取元素
    for(int i=0; i<s1.length();i++){
        cout<<s1.at(i)<<"  ";   //使用at可以抛出异常
    }
    return 0;
}

int main(){
    string s="abcd";
    printf("%s\n",s.c_str());   //获取字符串的首地址

    //将s中的内容copy到buf中
    char buf[128]={0};  //初始化空值
    s.copy(buf,3,0);
    cout<<"buf: "<<buf<<endl;

    //连接字符串
    string s1="aaa";
    string s2="bbb";
    string ss=s1+s2;
    string s3="1111";
    string s4="2222";
    s3.append(s4);
    cout<<"ss: "<<ss<<endl;
    cout<<"s3: "<<s3<<endl;
    return 0;
}

int main(){
    //字符串的查找与替换
    string s="hello, just enjoy the world,hello, just enjoy the world.hello, just enjoy the world.";
    int index=s.find("hello",0);    //从0的位置开始查找
    cout<<"index : "<<index<<endl;

    //求hello出现的次数
    int cindex=s.find("hello",0);
    while (cindex != string::npos) {
        cout<< "cindex: "<<cindex<<endl;
        s.replace(cindex,5,"HELLO");    //替换操作 从cindex号位置开始，将其中5哥字符换成”HELLO"
        cindex=s.find("hello",cindex+1);
    }
    cout<<s<<endl;
    return 0;
}

int main(){
    string s="hello, world,I hello am hello walking on hello the way";
    string::iterator it = find(s.begin(),s.end(),‘l‘);
    if (it != s.end()) {
        s.erase(it);
    }
    cout<<"s删除后的结果是： "<<s<<endl;
    //指定连续位置删除
    s.erase(s.begin()+7,s.begin()+15);
    cout<<"第二次删除： "<<s<<endl;

    string s2="afghi";
    s2.insert(1,"bcde");
    cout<<"s2: "<<s2<<endl;
    return 0;
}

int main(){
    string s1="AAAAbbbbccccDDDD";
    /* transform(b1,e1,b2,op)      //把一个区间[b1,e1)内的数据经过(op)转化,放入第二个容器内
     * 加上::的原因
     * The problem is that the version of std::tolower inherited from the C standard library is a non-template function,
     *  but there are other versions of std::tolower that are function templates,
     *  and it is possible for them to be included depending on the standard library implementation.
     *  You actually want to use the non-template function,
     * but there is ambiguity when just tolower is provided as the predicate.
     * 翻译过来就是说，既有C版本的toupper/tolower函数，又有STL模板函数toupper/tolower，二者存在冲突。
     */
    transform(s1.begin(),s1.end(),s1.begin(),::toupper);
    cout<<s1<<endl;
    return 0;
}