C++中的string类（C++字符串）入门完全攻略

typedef basic_string <char> string;

string s1(); // si = ""
string s2("Hello"); // s2 = "Hello"
string s3(4, 'K'); // s3 = "KKKK"
string s4("12345", 1, 3); //s4 = "234"，即 "12345" 的从下标 1 开始，长度为 3 的子串

string s1('K');
string s2(123);

string s1;
s1 = "Hello"; // s1 = "Hello"
s2 = 'K'; // s2 = "K”

string s1("12345"), s2;
s3.assign(s1); // s3 = s1
s2.assign(s1, 1, 2); // s2 = "23"，即 s1 的子串(1, 2)
s2.assign(4, 'K'); // s2 = "KKKK"
s2.assign("abcde", 2, 3); // s2 = "cde"，即 "abcde" 的子串(2, 3)

string s1("123"), s2("abc");
s1.append(s2); // s1 = "123abc"
s1.append(s2, 1, 2); // s1 = "123abcbc"
s1.append(3, 'K'); // s1 = "123abcbcKKK"
s1.append("ABCDE", 2, 3); // s1 = "123abcbcKKKCDE"，添加 "ABCDE" 的子串(2, 3)

string s1("hello"), s2("hello, world");
int n = s1.compare(s2);
n = s1.compare(1, 2, s2, 0, 3); //比较s1的子串 (1,2) 和s2的子串 (0,3)
n = s1.compare(0, 2, s2); // 比较s1的子串 (0,2) 和 s2
n = s1.compare("Hello");
n = s1.compare(1, 2, "Hello"); //比较 s1 的子串(1,2)和"Hello”
n = s1.compare(1, 2, "Hello", 1, 2); //比较 s1 的子串(1,2)和 "Hello" 的子串(1,2)

string substr(int n = 0, int m = string::npos) const;

string s1 = "this is ok";
string s2 = s1.substr(2, 4); // s2 = "is i"
s2 = s1.substr(2); // s2 = "is is ok"

string s1("West”), s2("East");
s1.swap(s2); // s1 = "East"，s2 = "West"

#include <iostream>
#include <string>
using namespace std;
int main()
{
 string s1("Source Code");
 int n;
 if ((n = s1.find('u')) != string::npos) //查找 u 出现的位置
  cout << "1) " << n << "," << s1.substr(n) << endl;
 //输出 l)2,urce Code
 if ((n = s1.find("Source", 3)) == string::npos)
  //从下标3开始查找"Source"，找不到
  cout << "2) " << "Not Found" << endl; //输出 2) Not Found
 if ((n = s1.find("Co")) != string::npos)
  //查找子串"Co"。能找到，返回"Co"的位置
  cout << "3) " << n << ", " << s1.substr(n) << endl;
 //输出 3) 7, Code
 if ((n = s1.find_first_of("ceo")) != string::npos)
  //查找第一次出现或 'c'、'e'或'o'的位置
  cout << "4) " << n << ", " << s1.substr(n) << endl;
 //输出 4) l, ource Code
 if ((n = s1.find_last_of('e')) != string::npos)
  //查找最后一个 'e' 的位置
  cout << "5) " << n << ", " << s1.substr(n) << endl; //输出 5) 10, e
 if ((n = s1.find_first_not_of("eou", 1)) != string::npos)
  //从下标1开始查找第一次出现非 'e'、'o' 或 'u' 字符的位置
  cout << "6) " << n << ", " << s1.substr(n) << endl;
 //输出 6) 3, rce Code
 return 0;
}

string s1("Real Steel");
s1.replace(1, 3, "123456", 2, 4); //用 "123456" 的子串(2,4) 替换 s1 的子串(1,3)
cout << s1 << endl; //输出 R3456 Steel
string s2("Harry Potter");
s2.replace(2, 3, 5, '0'); //用 5 个 '0' 替换子串(2,3)
cout << s2 << endl; //输出 HaOOOOO Potter
int n = s2.find("OOOOO"); //查找子串 "00000" 的位置，n=2
s2.replace(n, 5, "XXX"); //将子串(n,5)替换为"XXX"
cout << s2 < < endl; //输出 HaXXX Potter

string s1("Real Steel");
s1.erase(1, 3); //删除子串(1, 3)，此后 s1 = "R Steel"
s1.erase(5); //删除下标5及其后面的所有字符，此后 s1 = "R Ste"

string s1("Limitless"), s2("00");
s1.insert(2, "123"); //在下标 2 处插入字符串"123"，s1 = "Li123mitless"
s1.insert(3, s2); //在下标 2 处插入 s2 , s1 = "Li10023mitless"
s1.insert(3, 5, 'X'); //在下标 3 处插入 5 个 'X'，s1 = "Li1XXXXX0023mitless"

#include <iostream>
#include <sstream>
#include <string>
using namespace std;
int main()
{
  string src("Avatar 123 5.2 Titanic K");
  istringstream istrStream(src); //建立src到istrStream的联系
  string s1, s2;
  int n; double d; char c;
  istrStream >> s1 >> n >> d >> s2 >> c; //把src的内容当做输入流进行读取
  ostringstream ostrStream;
  ostrStream << s1 << endl << s2 << endl << n << endl << d << endl << c <<endl;
  cout << ostrStream.str();
  return 0;
}

#include <iostream>
#include <algorithm>
#include <string>
using namespace std;
int main()
{
  string s("afgcbed");
  string::iterator p = find(s.begin(), s.end(), 'c');
  if (p!= s.end())
    cout << p - s.begin() << endl; //输出 3
  sort(s.begin(), s.end());
  cout << s << endl; //输出 abcdefg
  next_permutation(s.begin(), s.end());
  cout << s << endl; //输出 abcdegf
  return 0;
}