string的使用

int main(){
  //声明并初始化一个空字符串
    string str1;
    
    //使用字符串字面量初始化字符串
  string str2 = "Hello Word!";
    
    //使用另一个string对象来初始化字符串
    string str3 = str2;
    
    //使用部分字符串初始化字符串
    string str4 = str2.substr(0, 5);//substr(起始位置，长度)
    
    //使用字符数组初始化字符串
    const char* charArray = "Hello";
    string str5(charArray);
    
    //使用重复的字符初始化字符串
    string str5(5, A);
    
    //输出字符串
    cout << str1 << endl;
    cout << str2 << endl;
    cout << str3 << endl;
    cout << str4 << endl;
    cout << str5 << endl;
    cout << str6 << endl;
    return 0;
}

string str = "Hello Word!";
int length  = str.length();
//或者int length = str.size();
cout << "length: " << length << endl;

string str1 = "Hello";
string str2 = "Word!";
result = str1 + "," + str2;//使用 + 运算符
result = str1.append(",").append(str2);//使用append函数
cout << result1 << endl;
cout << result2 << endl;

string str = "hello word!";
size_t pos = str.find("word");//查找子字符串的位置
if(pos != string :: nops){
    cout << pos << endl;
}else{
    cout << "not found" << endl;
}

string str = "hello word";
str.replace(7, 5, "Universe"); 
// 替换子字符串,7 表示起始位置，5 表示长度
cout << "result： " << str << endl;

string str = "hello word!";
string substr = str.substr(7, 5);//提取子字符串
cout << substr << endl;

string str1 = "hello";
string str2 = "word!";
int result = str1.compare(str2);//比较字符串
if(result == 0){
    cout << "string are equal." << endl;}
    else if(result < 0){
        cout << "string is less than string 2." << end;;
    }else {
        cout << "string is greater than string 2." << endl;
}

string s = "hello";
for(int i = 0; i < s.length(); ++i) cout << s[i] << end1;
for(auto i : s){
  cout << i;
    i = 'a';//此处的修改无效，因为这个i是拷贝出来的，而不是引用s的
} cout << '\n';
for(auto &i : s)
{
    cout << i;
    i = 'a'//此处修改会改变s的字符值
}
  cout << '\n';//此时s = "aaaaa"
  cout << s << endl;