详解C++中string的用法和例子

string s;//声明一个string 对象
string ss[10];//声明一个string对象的数组

#include <bits/stdc++.h>
using namespace std;
int main()
{
 ios::sync_with_stdio(false);
 string s;//默认初始化，一个空字符串
 string s1("ssss");//s1是字面值“ssss”的副本
 string s2(s1);//s2是s1的副本
 string s3=s2;//s3是s2的副本
 string s4(10,'c');//把s4初始化
 string s5="hiya";//拷贝初始化
 string s6=string(10,'c');//拷贝初始化，生成一个初始化好的对象，拷贝给s6
 //string s(cp,n)
 char cs[]="12345";
 string s7(cs,3);//复制字符串cs的前3个字符到s当中
 //string s(s2,pos2)
 string s8="asac";
 string s9(s8,2);//从s2的第二个字符开始拷贝，不能超过s2的size
 //string s(s2,pos2,len2)
 string s10="qweqweqweq";
 string s11(s10,3,4);//s4是s3从下标3开始4个字符的拷贝，超过s3.size出现未定义
 return 0;
}

#include <bits/stdc++.h>
using namespace std;
int main()
{
 ios::sync_with_stdio(false);
 string s="abcdefg";
 //s.substr(pos1,n)返回字符串位置为pos1后面的n个字符组成的串
 string s2=s.substr(1,5);//bcdef
 //s.substr(pos)//得到一个pos到结尾的串
 string s3=s.substr(4);//efg
 return 0;
}

#include <bits/stdc++.h>
using namespace std;
int main()
{
 ios::sync_with_stdio(false);
 string str="to be question";
 string str2="the ";
 string str3="or not to be";
 string::iterator it;
 //s.insert(pos,str)//在s的pos位置插入str
 str.insert(6,str2);     // to be the question
 //s.insert(pos,str,a,n)在s的pos位置插入str中插入位置a到后面的n个字符
 str.insert(6,str3,3,4);    // to be not the question
 //s.insert(pos,cstr,n)//在pos位置插入cstr字符串从开始到后面的n个字符
 str.insert(10,"that is cool",8); // to be not that is the question
 //s.insert(pos,cstr)在s的pos位置插入cstr
 str.insert(10,"to be ");   // to be not to be that is the question
 //s.insert(pos,n,ch)在s.pos位置上面插入n个ch
 str.insert(15,1,':');    // to be not to be: that is the question
 //s.insert(s.it,ch)在s的it指向位置前面插入一个字符ch，返回新插入的位置的迭代器
 it = str.insert(str.begin()+5,','); // to be, not to be: that is the question
 //s.insert(s.it,n,ch)//在s的it所指向位置的前面插入n个ch
 str.insert (str.end(),3,'.');  // to be, not to be: that is the question...
 //s.insert(it,str.ita,str.itb)在it所指向的位置的前面插入[ita,itb)的字符串
 str.insert (it+2,str3.begin(),str3.begin()+3); // to be, or not to be: that is the question...
 return 0;
}

#include <iostream>
#include <string>
int main ()
{
 std::string str ("This is an example sentence.");
 std::cout << str << '\n';
       // "This is an example sentence."
 str.erase (10,8);  //   ^^^^^^^^
 //直接指定删除的字符串位置第十个后面的8个字符
 std::cout << str << '\n';
       // "This is an sentence."
 str.erase (str.begin()+9);//   ^
 //删除迭代器指向的字符
 std::cout << str << '\n';
       // "This is a sentence."
       //  ^^^^^
 str.erase (str.begin()+5, str.end()-9);
 //删除迭代器范围的字符
 std::cout << str << '\n';
       // "This sentence."
 return 0;
}

#include <iostream>
#include <string>
int main ()
{
 std::string str;
 std::string str2="Writing ";
 std::string str3="print 10 and then 5 more";
 //直接追加一个str2的字符串
 str.append(str2);      // "Writing "
 //后面追加str3第6个字符开始的3个字符串
 str.append(str3,6,3);     // "10 "
 //追加字符串形参的前5个字符
 str.append("dots are cool",5);   // "dots "
 //直接添加
 str.append("here: ");     // "here: "
 //添加10个'.'
 str.append(10u,'.');     // ".........."
 //添加str3迭代器范围的字符串
 str.append(str3.begin()+8,str3.end()); // " and then 5 more"
 //最后这个比较特殊，意思是添加5个'A'，实际上参数里面的65对应的asc码就是65
 str.append<int>(5,65);    // "....."
 //字符串追加也可以用重载运算符实现
 str+="lalala";
 std::cout << str << '\n';
 return 0;
}

#include <iostream>
#include <string>
int main ()
{
 std::string base="this is a test string.";
 std::string str2="n example";
 std::string str3="sample phrase";
 std::string str4="useful.";
 // replace signatures used in the same order as described above:
 // Using positions:     0123456789*123456789*12345
 std::string str=base;   // "this is a test string."
 //第9个字符以及后面的4个字符被str2代替
 str.replace(9,5,str2);   // "this is an example string." (1)
 //第19个字符串以及后面的5个字符用str的第7个字符以及后面的5个字符代替
 str.replace(19,6,str3,7,6);  // "this is an example phrase." (2)
 //第8个字符以及后面的9个字符用字符串参数代替
 str.replace(8,10,"just a");  // "this is just a phrase."  (3)
 //第8个字符以及后面的5个字符用字符串参数的前7个字符替换
 str.replace(8,6,"a shorty",7); // "this is a short phrase." (4)
 //第22以及后面的0个字符用3个叹号替换
 str.replace(22,1,3,'!');  // "this is a short phrase!!!" (5)
 //迭代器的原理同上
 // Using iterators:            0123456789*123456789*
 str.replace(str.begin(),str.end()-3,str3);     // "sample phrase!!!"  (1)
 str.replace(str.begin(),str.begin()+6,"replace");    // "replace phrase!!!"  (3)
 str.replace(str.begin()+8,str.begin()+14,"is coolness",7); // "replace is cool!!!" (4)
 str.replace(str.begin()+12,str.end()-4,4,'o');    // "replace is cooool!!!" (5)
 str.replace(str.begin()+11,str.end(),str4.begin(),str4.end());// "replace is useful." (6)
 std::cout << str << '\n'; 
 return 0;
}

#include <iostream>
#include <string>
int main ()
{
 std::string str;
 std::string base="The quick brown fox jumps over a lazy dog.";
 // used in the same order as described above:
 //直接把base赋值给str
 str.assign(base);
 std::cout << str << '\n';
 //把base第10个字符以及后面的8个字符赋给str
 str.assign(base,10,9);
 std::cout << str << '\n';   // "brown fox"
 //把参数中的0到6个字符串赋给str
 str.assign("pangrams are cool",7);
 std::cout << str << '\n';   // "pangram"
 //直接使用参数赋值
 str.assign("c-string");
 std::cout << str << '\n';   // "c-string"
 //给str赋值10个'*'字符
 str.assign(10,'*');
 std::cout << str << '\n';   // "**********"
 //赋值是10个'-'
 str.assign<int>(10,0x2D);
 std::cout << str << '\n';   // "----------"
 //指定base迭代器范围的字符串
 str.assign(base.begin()+16,base.end()-12);
 std::cout << str << '\n';   // "fox jumps over"
 return 0;
}

#include <bits/stdc++.h>
using namespace std;
int main()
{
 ios::sync_with_stdio(false);
 std::string str ("There are two needles in this haystack with needles.");
 std::string str2 ("needle");
 // different member versions of find in the same order as above:
 //在str当中查找第一个出现的needle，找到则返回出现的位置，否则返回结尾
 std::size_t found = str.find(str2);
 if (found!=std::string::npos)
 std::cout << "first 'needle' found at: " << found << '\n';
 //在str当中，从第found+1的位置开始查找参数字符串的前6个字符
 found=str.find("needles are small",found+1,6);
 if (found!=std::string::npos)
 std::cout << "second 'needle' found at: " << found << '\n';
 //在str当中查找参数中的字符串
 found=str.find("haystack");
 if (found!=std::string::npos)
 std::cout << "'haystack' also found at: " << found << '\n';
 //查找一个字符
 found=str.find('.');
 if (found!=std::string::npos)
 std::cout << "Period found at: " << found << '\n';
 //组合使用，把str2用参数表中的字符串代替
 // let's replace the first needle:
 str.replace(str.find(str2),str2.length(),"preposition");
 std::cout << str << '\n';
 return 0;
}

#include <bits/stdc++.h>
using namespace std;
int main()
{
 ios::sync_with_stdio(false);
 std::string str ("The sixth sick sheik's sixth sheep's sick.");
 std::string key ("sixth");//     ^
 //rfind是找最后一个出现的匹配字符串
 std::size_t found = str.rfind(key);
 if (found!=std::string::npos)
 {
  cout<<found<<endl;//输出23
  str.replace (found,key.length(),"seventh");//找到的sixth替换成seventh
 }
 std::cout << str << '\n';
 return 0;
}

find_first_of(args) 查找args中任何一个字符第一次出现的位置
find_last_of(args) 最后一个出现的位置
find_fist_not_of(args) 查找第一个不在args中的字符
find_last_not_of 查找最后一个不在args中出现的字符
#include <bits/stdc++.h>
using namespace std;
int main()
{
 ios::sync_with_stdio(false);
 std::string str1 ("Please, replace the vowels in this sentence by asterisks.");
 std::size_t found1 = str1.find_first_of("aeiou");
 //把所有元音找出来用*代替
 while (found1!=std::string::npos)
 {
  str1[found1]='*';
  found1=str1.find_first_of("aeiou",found1+1);
 }
 std::cout << str1 << '\n';
 //在str2中找到第一个不是消协英文字母和空格的字符
 std::string str2 ("look for non-alphabetic characters...");
 std::size_t found2 = str2.find_first_not_of("abcdefghijklmnopqrstuvwxyz ");
 if (found2!=std::string::npos)
 {
  std::cout << "The first non-alphabetic character is " << str2[found2];
  std::cout << " at position " << found2 << '\n';
 }
 return 0;
}

#include <bits/stdc++.h>
using namespace std;
int main()
{
 ios::sync_with_stdio(false);
 string s1="123",s2="123";
 cout<<s1.compare(s2)<<endl;//0
 s1="123",s2="1234";
 cout<<s1.compare(s2)<<endl;//-1
 s1="1234",s2="123";
 cout<<s1.compare(s2)<<endl;//1
 std::string str1 ("green apple");
 std::string str2 ("red apple");
 if (str1.compare(str2) != 0)
 std::cout << str1 << " is not " << str2 << '\n';
 //str1的第6个字符以及后面的4个字符和参数比较
 if (str1.compare(6,5,"apple") == 0)
 std::cout << "still, " << str1 << " is an apple\n";
 if (str2.compare(str2.size()-5,5,"apple") == 0)
 std::cout << "and " << str2 << " is also an apple\n";
 //str1的第6个字符以及后面的4个字符和str2的第4个字符以及后面的4个字符比较
 if (str1.compare(6,5,str2,4,5) == 0)
 std::cout << "therefore, both are apples\n";
 return 0;
}

//注意，下段代码在MinGw中会报错！即使使用c++11编译也一样，无法识别to_string！
#include <bits/stdc++.h>
using namespace std;
int main()
{
 ios::sync_with_stdio(false);
 string s1;
 s1=to_string(100);
 cout<<s1<<endl;
 int a=stoi(s1,0,10)+1;
 cout<<a<<endl;
 return 0;
}