STL 小白学习（2） string

#include <iostream>
using namespace std;
#include <string>


//初始化操作
void test01() {
    //初始化操作
    string s1;
    string s2(10, 'a');
    string s3("abc");
    string s4(s3);

    cout << s1 << endl;
    cout << s2 << endl;
    cout << s3 << endl;
    cout << s4 << endl;


}    
//赋值操作
void test02() {
    //赋值操作
    string s1;
    string s2("appasd");
    s1 = "132456";
    cout << s1 << endl;
    s1 = s2;
    cout << s1 << endl;
    s1 = 'a';
    cout << s1 << endl;

    //成员方法 assign
    s1.assign("jsk");
    cout << s1 << endl;
     
}

//取值操作
void test03() {
    //取值操作
    string s1 = "abashjdsa";

    //重载[]操作符
    for (int i = 0; i < s1.size(); i++) {
        cout << s1[i] << " ";
    }
    cout << endl;

    //也提供了成员方法
    for (int i = 0; i < s1.size(); i++) {
        cout << s1.at(i) << " ";
    }
    cout << endl;

    //区别
    //[] 访问越界直接挂
    //at(i) 抛出异常
    try {
        cout << s1.at(100)<<endl;
    }
    catch (...) {
        cout << "越界 Error...！" << endl;
    }

}
//拼接操作
void test04() {
    //+= 重载
    string s = "123";
    cout << s << endl;
    s += "456";
    cout << s << endl;
    string s2 = "abc";
    s += s2;
    cout << s << endl;
    //append 成员函数重载
    string s3 = "23";
    s.append(s3);
    cout << s << endl;
    //等号重载
    string s4 = s + s3;
    cout << s4 << endl;

}

//string 查找与替换
void test05() {
    string s = "fgabcdefg";
    //s.find 查找第一次出现的位置
    int pos = s.find("z");
    cout << "pos: " << pos << endl;//没有 return -1
    //s.rfind 查找最后一次出现的位置
    pos = s.rfind('g');
    cout << "pos: " << pos << endl;
    

}
//替换
void test06() {
    //替换
    string s = "abcdefg";
    s.replace(0, 2, "1111"); //将0位置开始的2个 ab替换成1111
    cout << s << endl;
}
//比较
void test07() {
    //比较 相等返回0
    string s1 = "abcd";
    string s2 = "abc4";

    if (s1.compare(s2) == 0) {
        cout << "相等" << endl;
    }
    else {
        cout << "不相等！" << endl;
    }

}
//字串操作
void test08() {
    string s = "abcsdsfsadas";
    string substring = s.substr(1, 3);//取s的从1位置开始的3个字符的字串
    cout << substring << endl;

}
//插入 删除
void test09() {
    string s = "asfasddfsa";
    s.insert(1, "123");//在s[1]位置前插入123
    cout << s << endl;
    s = "1423999";
    s.erase(0, 4);//删除 s[0]开始的4个字符
    cout << s << endl;
}
int main() {
    test09();
}