5. string类非成员函数

上面的几个接口大家了解一下，下面的OJ题目中会有一些体现他们的使用。string类中还有一些其他的 操作，这里不一一列举，大家在需要用到时不明白了查文档即可。

试用rfind、substr、find、find_first_(not)_of

void test_string9()
{//string s1("file.cpp");string s1("file.c.tar.zip");// 拿到文件的后缀size_t pos1 = s1.rfind('.');if (pos1 != string::npos){string suffix = s1.substr(pos1);//string suffix = s1.substr(pos1, s1.size()-pos1);cout << suffix << endl;}else{cout << "没有后缀" << endl;}string url2("https://legacy.cplusplus.com/reference/string/string/substr/");string url1("http://www.baidu.com/s?ie=utf-8&f=8&rsv_bp=1&rsv_idx=1&tn=65081411_1_oem_dg&wd=%E5%90%8E%E7%BC%80%20%E8%8B%B1%E6%96%87&fenlei=256&rsv_pq=0xc17a6c03003ede72&rsv_t=7f6eqaxivkivsW9Zwc41K2mIRleeNXjmiMjOgoAC0UgwLzPyVm%2FtSOeppDv%2F&rqlang=en&rsv_dl=ib&rsv_enter=1&rsv_sug3=4&rsv_sug1=3&rsv_sug7=100&rsv_sug2=0&rsv_btype=i&inputT=1588&rsv_sug4=6786");string protocol, domain, uri;size_t i1 = url1.find(':');if (i1 != string::npos){protocol = url1.substr(0, i1 - 0);cout << protocol << endl;}// strcharsize_t i2 = url1.find('/', i1 + 3);if (i2 != string::npos){domain = url1.substr(i1 + 3, i2 - (i1 + 3));cout << domain << endl;uri = url1.substr(i2 + 1);cout << uri << endl;}// strstrsize_t i3 = url1.find("baidu");cout << i3 << endl;std::string str("Please, replace the vowels in this sentence by asterisks.");cout << str << endl;// strtokstd::size_t found = str.find_first_not_of("aeiou");while (found != std::string::npos){str[found] = '*';found = str.find_first_not_of("aeiou", found + 1);}cout << str << endl;cout << (url1 < url2) << endl;string ss1 = "xxx";string ss2 = "yyy";string ret = ss1 + ss2;cout << ret << endl;string ret1 = ss1 + "yyyy";string ret2 = "yyyy" + ss2;
}

试用assign、insert、erase、swap

void test_string10()
{string s1("xhello world");cout << s1 << endl;s1.assign(" xxxxx");cout << s1 << endl;s1.insert(0, "yyyy");cout << s1 << endl;s1.erase(5, 3);cout << s1 << endl;s1.erase();cout << s1 << endl;string s2("hello world hello bit");/*s2.replace(5, 1, "20%");cout << s2 << endl;*//*size_t pos = s2.find(' ');while (pos != string::npos){s2.replace(pos, 1, "20%");pos = s2.find(' ');}cout << s2 << endl;*/// insert/erase/replace// 能少用就要少用，因为基本都要挪动数据，效率不高string s3;s3.reserve(s2.size());for (auto ch : s2){if (ch != ' '){s3 += ch;}else{s3 += "20%";}}cout << s3 << endl;s2.swap(s3);cout << s2 << endl;
}