C++/String/string compare — различия между версиями
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Текущая версия на 10:25, 25 мая 2010
Содержание
- 1 Compare string ignoring the case
- 2 Compare strings
- 3 Compare strings by index: string1.compare( 2, 5, string3, 0, 5)
- 4 Compare sub string: string4.compare( 0, string2.length(), string2 )
- 5 return true if c1
- 6 return true if c1 equals c2 (regardless of case), false otherwise
- 7 Set with functor for string comparison
- 8 String: equals
- 9 string overloaded equality and relational operators
- 10 Use == > and
- 11 Use std::lexicographical_compare to compare two char arrays
- 12 Use string.compare to compare two strings
Compare string ignoring the case
#include <string>
#include <iostream>
#include <algorithm>
#include <cctype>
#include <cwctype>
using namespace std;
inline bool caseInsCharCompareN(char a, char b) {
return(toupper(a) == toupper(b));
}
bool caseInsCompare(const string& s1, const string& s2) {
return((s1.size( ) == s2.size( )) &&
equal(s1.begin( ), s1.end( ), s2.begin( ), caseInsCharCompareN));
}
int main( ) {
string s1 = "In the BEGINNING...";
string s2 = "In the beginning...";
if (caseInsCompare(s1, s2))
cout << "Equal!\n";
}
/*
Equal!
*/
Compare strings
#include <string>
#include <iostream>
using namespace std;
int main(int argc, char** argv)
{
string myString = "hello";
myString += ", there";
string str2 = myString;
if (myString == str2) {
str2[0] = "H";
}
cout << myString << endl;
cout << str2 << endl;
}
Compare strings by index: string1.compare( 2, 5, string3, 0, 5)
#include <iostream>
using std::cout;
using std::endl;
#include <string>
using std::string;
int main()
{
string string1( "AAAAAAAAAAAAAA" );
string string2( "BBBBBBBBBBBBBB" );
string string3( "CCCCCCCCCCCCCC" );
string string4( string2 );
cout << "string1: " << string1 << "\nstring2: " << string2
<< "\nstring3: " << string3 << "\nstring4: " << string4 << "\n\n";
// comparing string1 (elements 2-5) and string3 (elements 0-5)
int result = string1.compare( 2, 5, string3, 0, 5 );
if ( result == 0 )
cout << "string1.compare( 2, 5, string3, 0, 5 ) == 0\n";
else {
if ( result > 0 )
cout << "string1.compare( 2, 5, string3, 0, 5 ) > 0\n";
else
cout << "string1.compare( 2, 5, string3, 0, 5 ) < 0\n";
}
return 0;
}
/*
string1: AAAAAAAAAAAAAA
string2: BBBBBBBBBBBBBB
string3: CCCCCCCCCCCCCC
string4: BBBBBBBBBBBBBB
string1.compare( 2, 5, string3, 0, 5 ) < 0
*/
Compare sub string: string4.compare( 0, string2.length(), string2 )
#include <iostream>
using std::cout;
using std::endl;
#include <string>
using std::string;
int main()
{
string string1( "AAAAAAAAAAAAAA" );
string string2( "BBBBBBBBBBBBBB" );
string string3( "CCCCCCCCCCCCCC" );
string string4( string2 );
cout << "string1: " << string1 << "\nstring2: " << string2
<< "\nstring3: " << string3 << "\nstring4: " << string4 << "\n\n";
// comparing string2 and string4
int result = string4.compare( 0, string2.length(), string2 );
if ( result == 0 )
cout << "string4.compare( 0, string2.length(), " << "string2 ) == 0" << endl;
else {
if ( result > 0 )
cout << "string4.compare( 0, string2.length(), " << "string2 ) > 0" << endl;
else
cout << "string4.compare( 0, string2.length(), "
<< "string2 ) < 0" << endl;
}
return 0;
}
/*
string1: AAAAAAAAAAAAAA
string2: BBBBBBBBBBBBBB
string3: CCCCCCCCCCCCCC
string4: BBBBBBBBBBBBBB
string4.compare( 0, string2.length(), string2 ) == 0
*/
return true if c1
#include <algorithm>
#include <cctype>
#include <iostream>
#include <string>
using namespace std;
// return true if c1 < c2 (ignoring case), false otherwise
bool less_than_insensitive( char c1, char c2 )
{
return tolower( static_cast<unsigned char>( c1 ) ) < tolower( static_cast<unsigned char>( c2 ) );
}
int main( )
{
}
return true if c1 equals c2 (regardless of case), false otherwise
#include <algorithm>
#include <cctype>
#include <iostream>
#include <string>
using namespace std;
// return true if c1 equals c2 (regardless of case), false otherwise
bool equal_to_insensitive( char c1, char c2 ){
return tolower( static_cast<unsigned char>( c1 ) ) == tolower( static_cast<unsigned char>( c2 ) );
}
int main( )
{
}
Set with functor for string comparison
#include <iostream>
#include <set>
#include <string>
#include <functional>
#include <cassert>
using namespace std;
struct strPtrLess {
bool operator( )(const string* p1,const string* p2) {
return(*p1 < *p2);
}
};
int main( ) {
set<string*, strPtrLess> setStrPtr; // less-than functor
string s1 = "T";
string s2 = "D";
string s3 = "H";
setStrPtr.insert(&s1);
setStrPtr.insert(&s2);
setStrPtr.insert(&s3);
for (set<string*, strPtrLess>::const_iterator p = setStrPtr.begin( ); p != setStrPtr.end( ); ++p)
cout << **p << endl;
}
/*
D
H
T
*/
String: equals
#include <iostream.h>
#include <string>
using std::string;
main(void)
{
string s1 = "abcdefghijk", s2 = "1234567890", s3,s4,s5;
s3=s1+s2;
cout << s3 <<endl;
s4=s3;
if (s4==s3)
cout << " s4==s3 is true\n";
return(0);
}
/*
abcdefghijk1234567890
s4==s3 is true
*/
string overloaded equality and relational operators
#include <iostream>
using std::cout;
using std::endl;
#include <string>
using std::string;
int main()
{
string s1( "AA" );
string s2( " AAB" );
string s3;
//
cout << "s1 is \"" << s1 << "\"; s2 is \"" << s2
<< "\"; s3 is \"" << s3 << "\""
<< "\n\nThe results of comparing s2 and s1:"
<< "\ns2 == s1 yields " << ( s2 == s1 ? "true" : "false" )
<< "\ns2 != s1 yields " << ( s2 != s1 ? "true" : "false" )
<< "\ns2 > s1 yields " << ( s2 > s1 ? "true" : "false" )
<< "\ns2 < s1 yields " << ( s2 < s1 ? "true" : "false" )
<< "\ns2 >= s1 yields " << ( s2 >= s1 ? "true" : "false" )
<< "\ns2 <= s1 yields " << ( s2 <= s1 ? "true" : "false" );
return 0;
}
/*
s1 is "AA"; s2 is " AAB"; s3 is ""
The results of comparing s2 and s1:
s2 == s1 yields false
s2 != s1 yields true
s2 > s1 yields false
s2 < s1 yields true
s2 >= s1 yields false
s2 <= s1 yields true
*/
Use == > and
#include <iostream>
using std::cout;
using std::endl;
#include <string>
using std::string;
int main()
{
string string1( "AAAAAAAAAAAAAA" );
string string2( "BBBBBBBBBBBBBB" );
string string3( "CCCCCCCCCCCCCC" );
string string4( string2 );
cout << "string1: " << string1 << "\nstring2: " << string2
<< "\nstring3: " << string3 << "\nstring4: " << string4 << "\n\n";
// comparing string1 and string4
if ( string1 == string4 )
cout << "string1 == string4\n";
else{
if ( string1 > string4 )
cout << "string1 > string4\n";
else // string1 < string4
cout << "string1 < string4\n";
}
return 0;
}
/*
string1: AAAAAAAAAAAAAA
string2: BBBBBBBBBBBBBB
string3: CCCCCCCCCCCCCC
string4: BBBBBBBBBBBBBB
string1 < string4
*/
Use std::lexicographical_compare to compare two char arrays
#include <iostream>
using std::cout;
using std::endl;
#include <algorithm>
#include <vector>
#include <iterator>
int main()
{
char c1[ 10 ] = "HELLO";
char c2[ 10 ] = "BYE BYE";
// perform lexicographical comparison of c1 and c2
bool result = std::lexicographical_compare( c1, c1 + 10, c2, c2 + 10 );
cout << c1 << ( result ? " is less than " :
" is greater than or equal to " ) << c2 << endl;
return 0;
}
/*
HELLO is greater than or equal to BYE BYE
*/
Use string.compare to compare two strings
#include <iostream>
using std::cout;
using std::endl;
#include <string>
using std::string;
int main()
{
string string1( "AAAAAAAAAAAAAA" );
string string2( "BBBBBBBBBBBBBB" );
string string3( "CCCCCCCCCCCCCC" );
string string4( string2 );
cout << "string1: " << string1 << "\nstring2: " << string2
<< "\nstring3: " << string3 << "\nstring4: " << string4 << "\n\n";
// comparing string1 and string2
int result = string1.compare( string2 );
if ( result == 0 )
cout << "string1.compare( string2 ) == 0\n";
else {
if ( result > 0 )
cout << "string1.compare( string2 ) > 0\n";
else
cout << "string1.compare( string2 ) < 0\n";
}
return 0;
}
/*
string1: AAAAAAAAAAAAAA
string2: BBBBBBBBBBBBBB
string3: CCCCCCCCCCCCCC
string4: BBBBBBBBBBBBBB
string1.compare( string2 ) < 0
*/