C++中string容器的字符串操作

admin2024-04-03  0

目录

1.c_str() 返回C常量字符串

2.date() 返回C常量字符串

3.substr() 构造子串

4.find() 正向查找(查找失败返回npos)

5.rfind() 逆向查找(查找失败返回npos)

6.find_first_of() 正向查找匹配的字符

7.find_last_of() 逆向查找匹配的字符

8.find_first_not_of() 正向查找不匹配的字符

9.find_last_not_of() 逆向查找不匹配的字符

10.compare() 比较字符串


1.c_str() 返回C常量字符串

const char* c_str() const 

string s("123");
const char* p = s.c_str();
cout << p << endl;//123

2.date() 返回C常量字符串

const char* data() const

string s("12345");
const char* p = s.data();
cout << p << endl;//12345

3.substr() 构造子串

string substr(size_t pos = 0, size_t len = npos) const 

返回pos位置开始的len个字符组成的字符串

string s1 = "12345";
string s2 = s1.substr(2, 3);
cout << s2 << endl;//345

4.find() 正向查找(查找失败返回npos)

string (1)
size_t find (const string& str, size_t pos = 0) const;
c-string (2)
size_t find (const char* s, size_t pos = 0) const;
buffer (3)
size_t find (const char* s, size_t pos, size_t n) const;
character (4)
size_t find (char c, size_t pos = 0) const;

1.size_t find(const string& str, size_t  pos = 0) const 

从pos位置开始查找匹配的对象str,返回查找到的位置

2.size_t find(const char* s, size_t pos = 0) const 

从pos位置开始查找匹配的字符串s,返回查找到的位置

3.size_t find(const char* s, size_t pos, size_t n)

从pos位置查找匹配字符串s的前n个字符,返回查找到的位置

4.size_t find(char c, size_t pos = 0)

从pos位置开始查找字符c,返回查找到的位置

string s1("There are two needles in this haystack with needles.");
string s2("needle");
size_t found = s1.find(s2, 0);
if (found != string::npos)
{
	cout << "first 'needle' found at " << found << endl;//first 'needle' found at 14
}
else
{
	cout << "'needle' no found" << endl;
}

found = s1.find("needle are small", found + 1, 6);
if (found != string::npos)
{
	cout << "second 'needle' found at " << found << endl;//second 'needle' found at 44
}
else
{
	cout << "'needle' no found" << endl;
}

found = s1.find("haystack", 0);
if (found != string::npos)
{
	cout << "'haystack' found at " << found << endl;//'haystack' found at 30
}
else
{
	cout << "'haystack' no found" << endl;
}

found = s1.find('.', 0);
if (found != string::npos)
{
	cout << "'.' found at " << found << endl;//'.' found at 30
}
else
{
	cout << "'.' no found" << endl;
}

5.rfind() 逆向查找(查找失败返回npos)

string (1)
size_t rfind (const string& str, size_t pos = npos) const;
c-string (2)
size_t rfind (const char* s, size_t pos = npos) const;
buffer (3)
size_t rfind (const char* s, size_t pos, size_t n) const;
character (4)
size_t rfind (char c, size_t pos = npos) const;

1.size_t rfind(const string& str, size_t pos =npos) const

从pos位置逆向开始查找匹配的对象str,返回查找到的位置

2.size_t rfind(const char* s, size_t pos =npos) const

从pos位置逆向开始查找匹配的字符串s,返回查找到的位置

3.size_t rfind(const char* s, size_t pos, size_t n) const

从pos位置逆向查找匹配字符串s的前n个字符,返回查找到的位置

4.size_t rfind(char c, size_t pos =npos) const

从pos位置逆向开始查找字符c,返回查找到的位置

string str("The sixth sick sheik's sixth sheep's sick.");
string key("sixth");
size_t found = str.rfind(key);
if (found != string::npos)
	cout << "'sixth' found at " << found << endl;//'sixth' found at 23

6.find_first_of() 正向查找匹配的字符

正向查找首个与指定字符串中任一字符匹配的字符,查找失败返回npos

string (1)
size_t find_first_of (const string& str, size_t pos = 0) const;
c-string (2)
size_t find_first_of (const char* s, size_t pos = 0) const;
buffer (3)
size_t find_first_of (const char* s, size_t pos, size_t n) const;
character (4)
size_t find_first_of (char c, size_t pos = 0) const;

1.size_t find_first_of(const string& str, size_t pos = 0) const 

从pos位置开始查找对象str中首次出现的任一字符,查找失败返回npos

2.size_t find_first_of(const char* s, size_t pos = 0) const

从pos位置开始查找字符串s中出现的任一字符,查找失败返回npos

3.size_t find_first_of(const char* s, size_t pos, size_t n) const 

从pos位置开始查找字符串s的前n个字符串中出现的任一字符,查找失败返回npos

4.size_t find_first_of(char c, size_t pos =0 ) const 

从pos位置开始查找首次出现的字符c,查找失败返回npos

string s("Please, replace the vowels in this sentence by asterisks.");
size_t found = s.find_first_of("aoeiu", 0);
while (found != string::npos)
{
	s[found] = '*';
	found = s.find_first_of("aoeiu", found + 1);
}
cout << s << endl;//Pl**s*, r*pl*c* th* v*w*ls *n th*s s*nt*nc* by *st*r*sks.

7.find_last_of() 逆向查找匹配的字符

逆向查找首个与指定字符串中任一字符匹配的字符,查找失败返回npos

string (1)
size_t find_last_of (const string& str, size_t pos = npos) const;
c-string (2)
size_t find_last_of (const char* s, size_t pos = npos) const;
buffer (3)
size_t find_last_of (const char* s, size_t pos, size_t n) const;
character (4)
size_t find_last_of (char c, size_t pos = npos) const;

1.size_t find_last_of(const string& str, size_t pos = npos) const

从pos位置开始逆向查找首个与对象str中任一字符匹配的字符,查找失败返回npos

2.size_t find_last_of(const char* s, size_t pos = npos) const

ni从pos位置开始逆向查找首个与字符串s中任意字符匹配的字符,查找失败返回npos

3.size_t find_last_of(const char* s,size_t pos, size_t n) const

从pos位置开始逆向查找首个与字符串s的前n个字符中任意字符匹配的字符,查找失败返回npos

4.size_t find_last_of(char c, size_t pos =npos) const

ni从pos位置开始逆向查找首个与字符c匹配的字符,查找失败返回npos

void SplitFilename(const string& str)
{
	size_t found = str.find_last_of("/\");
	cout << "path :" << str.substr(0, found) << endl;
	cout << "file :" << str.substr(found + 1) << endl;
}
void string_test()
{
	string s1("/usr/bin/man");
	string s2("c:\windows\winhelp.exe");
	SplitFilename(s1);
	SplitFilename(s2);

}
int main()
{
	string_test();
	//path: / usr / bin
	//file : man
	//path : c:\windows
	//file : winhelp.exe
	return 0;
}

 8.find_first_not_of() 正向查找不匹配的字符

正向查找首个与指定字符串中任一字符不匹配的字符,查找失败返回npos

string (1)
size_t find_first_not_of (const string& str, size_t pos = 0) const;
c-string (2)
size_t find_first_not_of (const char* s, size_t pos = 0) const;
buffer (3)
size_t find_first_not_of (const char* s, size_t pos, size_t n) const;
character (4)
size_t find_first_not_of (char c, size_t pos = 0) const;

1.size_t find_first_not_of(const string& str, size_t pos = 0) const 

从pos位置开始正向查找首个与对象str中字符不匹配的字符,查找失败返回npos

2.size_t find_first_not_of(const char* s, size_t pos = 0) const

从pos位置开始正向查找首个与字符串s中字符不匹配的字符,查找失败返回npos

3.size_t find_first_not_of(const char* s, size_t pos, size_t n) const

从pos位置开始正向查找首个与字符串s前n个字符中字符不匹配的字符,查找失败返回npos

4.size_t find_first_not_of(char c, size_t pos = 0) const

从pos位置开始正向查找首个与字符c不匹配的字符,查找失败返回npos

string str("look for non-alphabetic characters...");
size_t found = str.find_first_not_of("abcdefghijklmnopqrstuvwxyz ");
if (found != string::npos)
{
	cout << "The first non-alphabetic character is " << str[found] << " at position " << found << endl;
	//The first non-alphabetic character is - at position 12
}

9.find_last_not_of() 逆向查找不匹配的字符

 逆向查找首个与指定字符串中任一字符不匹配的字符,查找失败返回npos

string (1)
size_t find_last_not_of (const string& str, size_t pos = npos) const;
c-string (2)
size_t find_last_not_of (const char* s, size_t pos = npos) const;
buffer (3)
size_t find_last_not_of (const char* s, size_t pos, size_t n) const;
character (4)
size_t find_last_not_of (char c, size_t pos = npos) const;

1.size_t find_last_not_of(const string& str, size_t pos = npos) const

从pos位置开始逆向查找首个与对象str中字符不匹配的字符,查找失败返回npos

2.size_t find_last_not_of(const char* s, size_t pos = npos) const

从pos位置开始逆向查找首个与字符串s中字符不匹配的字符,查找失败返回npos

3.size_t find_last_not_of(const char* s, size_t pos, size_t n) const

从pos位置开始逆向查找首个与字符串s前n个字符中字符不匹配的字符,查找失败返回npos

4.size_t find_last_not_of(char c, size_t pos = npos) const

从pos位置开始逆向查找首个与字符c不匹配的字符,查找失败返回npos

string str("Please, erase trailing white-spaces   \n");
string whitespaces(" \t\f\v\n\r");
size_t found = str.find_last_not_of(whitespaces);
if (found != string::npos)
    str.erase(found + 1);   
    //[Please, erase trailing white-spaces]
else
    str.clear();
cout << "[" << str << "]" << endl;

10.compare() 比较字符串

比较两个字符串的ASCII码值,字符串1大于字符串2返回大于0的数;字符串1等于字符串2返回0;字符串1小于字符串2返回小于0的数

string (1)
int compare (const string& str) const;
substrings (2)
int compare (size_t pos, size_t len, const string& str) const;
int compare (size_t pos, size_t len, const string& str,
             size_t subpos, size_t sublen) const;
c-string (3)
int compare (const char* s) const;
int compare (size_t pos, size_t len, const char* s) const;
buffer (4)
int compare (size_t pos, size_t len, const char* s, size_t n) const;

1.int compare(const string& str) const

比较调用对象和str对象的大小

2.int compare(size_t pos, size_t len, const string& str) const

比较调用对象pos位置开始的len个字符与对象str的大小

int compare(size_t pos, size_t len, const string& str, size_t subpos, size_t sublen) const

比较调用对象pos位置开始的len个字符与对象str中subpos位置开始的sublen个字符的大小

3.int compare(const char* s) const

比较调用对象和字符串s的大小

int compare(size_t pos, size_t len, const char* s) const

比较调用对象从pos位置开始的len个字符与字符串s的大小

4.int compare(size_t pos, size_t len, const char* s, size_t n) const

比较调用对象从pos位置开始的len个字符与字符串s前n个字符的大小

//1.
string s1("abcdefg");
string s2("abcdfg");
if (s1.compare(s2) == 0)
	cout << s1 << " = " << s2 << endl;
else if (s1.compare(s2) > 0)
	cout << s1 << " > " << s2 << endl;
else
	cout << s1 << " < " << s2 << endl; //abcdefg < abcdfg

//2.1
string s1("abcdefg");
string s2("abcdfg");
if (s1.compare(1, 6, s2) == 0)
	cout << s1 << " = " << s2 << endl;
else if (s1.compare(1, 6, s2) > 0)
	cout << s1 << " > " << s2 << endl;//abcdefg > abcdfg
else
	cout << s1 << " < " << s2 << endl; 

//2.2
string s1("abcdefg");
string s2("abcdfg");
if (s1.compare(1, 6, s2, 1, 5) == 0)
	cout << s1 << " = " << s2 << endl;
else if (s1.compare(1, 6, s2, 1, 5) > 0)
	cout << s1 << " > " << s2 << endl;
else
	cout << s1 << " < " << s2 << endl;//abcdefg < abcdfg

//3.1
string s("abcdefg");
char p[] = "abcdfg";
if (s.compare(p) == 0)
	cout << s << " = " << p << endl;
else if (s.compare(p) > 0)
	cout << s << " > " << p << endl;
else
	cout << s << " < " << p << endl;//abcdefg < abcdfg

//3.2
string s("abcdefg");
char p[] = "abcdfg";
if (s.compare(1, 5, p) == 0)
	cout << s << " = " << p << endl;
else if (s.compare(1, 5, p) > 0)
	cout << s << " > " << p << endl;//abcdefg > abcdfg
else
	cout << s << " < " << p << endl;

//4
string s("abcdefg");
char p[] = "abcdfg";
if (s.compare(1, 5, p, 5) == 0)
	cout << s << " = " << p << endl;
else if (s.compare(1, 5, p, 5) > 0)
	cout << s << " > " << p << endl;//abcdefg > abcdfg
else
	cout << s << " < " << p << endl;
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