sammenligne() er en offentlig medlemsfunktion af strengklasse. Den sammenligner værdien af ​​strengobjektet (eller en understreng) med sekvensen af ​​tegn, der er specificeret af dets argumenter.
Compare() kan behandle mere end ét argument for hver streng, så man kan specificere en understreng ved dets indeks og ved dets længde.
Returtype: compare() returnerer en heltalsværdi i stedet for en boolsk værdi.
Forskellige syntakser for streng::compare() :

Syntaks 1: Sammenligner strengen *dette med strengen str.

 int string::compare (const string& str) const Returns: 0 : if both strings are equal. A value  <0 :  if *this is shorter than str or, first character that doesn't match is smaller than str. A value>0 : hvis *dette er længere end str eller, er det første tegn, der ikke matcher, større 

CPP

// CPP code for demonstrating> // string::compare (const string& str) const> #include> using> namespace> std;> void> compareOperation(string s1, string s2)> {> > // returns a value <0 (s1 is smaller than s2)> > if> ((s1.compare(s2)) <0)> > cout < < s1 < < ' is smaller than ' < < s2 < < endl;> > // returns 0(s1, is being compared to itself)> > if> ((s1.compare(s1)) == 0)> > cout < < s1 < < ' is equal to ' < < s1 < < endl;> > else> > cout < < 'Strings didn't match ';> > }> // Driver Code> int> main()> {> > string s1('Geeks');> > string s2('forGeeks');> > compareOperation(s1, s2);> > > return> 0;> }>

Produktion:

Geeks is smaller than forGeeks Geeks is equal to Geeks 

Syntaks 2: Sammenligner højst len-tegn i streng *dette, startende med index idx med strengen str.

 int string::compare (size_type idx, size_type len, const string& str) const Throws out_of_range if index>størrelse(). 

CPP

// CPP code to demonstrate> // int string::compare (size_type idx, size_type len,> // const string& str) const> #include> using> namespace> std;> void> compareOperation(string s1, string s2)> {> > // Compares 5 characters from index number 3 of s2 with s1> > if> ((s2.compare(3, 5, s1)) == 0)> > cout < < 'Here, ' < < s1 < < ' are ' < < s2;> > else> > cout < < 'Strings didn't match ';> }> // Driver Code> int> main()> {> > string s1('Geeks');> > string s2('forGeeks');> > compareOperation(s1, s2);> > > return> 0;> }>

Produktion:

Here, Geeks are forGeeks 

Syntaks 3: Sammenligner højst len-tegn i streng *dette starter med index idx med højst str_len-tegn i streng str, der starter med index str_idx.

 int string::compare (size_type idx, size_type len, const string&  str, size_type str_idx, size_type str_len) const Throws out_of_range if idx>størrelse(). Kaster out_of_range hvis str_idx> str.size(). 

CPP

// CPP code to demonstrate> // int string::compare (size_type idx, size_type len, const string&> // str, size_type str_idx, size_type str_len) const> #include> using> namespace> std;> void> compareOperation(string s1, string s2)> {> > // Compares 5 characters from index number 0 of s1 with> > // 5 characters from index 3 of s2> > if> ((s1.compare(0, 5, s2, 3, 5)) == 0)> > cout < < 'Welcome to ' < < s1 < < s2 < < ' World';> > else> > cout < < 'Strings didn't match ';> }> // Driver Code> int> main()> {> > string s1('Geeks');> > string s2('forGeeks');> > compareOperation(s1, s2);> > > return> 0;> }>

Produktion:

Welcome, to techcodeview.com World 

Syntaks 4: Sammenligner tegnene i streng *dette med tegnene i C-strengen cstr.

 int string::compare (const char* cstr) const 

CPP

// CPP code to demonstrate> // int string::compare (const char* cstr) const> #include> using> namespace> std;> void> compareOperation(string s1, string s2)> {> > // returns <0 (s1 < 'techcodeview.com')> > if> ((s1.compare('techcodeview.com')) <0)> > cout < < s1 < < ' is smaller than string ' < < 'techcodeview.com';> > //returns 0 (s2 is 'forgeeks')> > if> ((s2.compare('forGeeks')) == 0)> > cout < < endl < < s2 < < ' is equal to string ' < < s2;> > else> > cout < < 'Strings didn't match ';> > }> // Driver Code> int> main()> {> > string s1('Geeks');> > string s2('forGeeks');> > compareOperation(s1, s2);> > > return> 0;> }>

Produktion:

Geeks is smaller than string techcodeview.com forGeeks is equal to string forGeeks 

Syntaks 5: Sammenligner højst len-tegn i streng *dette, startende med index idx med alle tegn i C-strengen cstr.

 int string::compare (size_type idx, size_type len, const char* cstr) const 

Bemærk, at cstr muligvis ikke er en nul-pointer (NULL).

CPP

// CPP code to demonstrate> // int string::compare (size_type idx, size_type len,> // const char* cstr) const> #include> using> namespace> std;> void> compareOperation(string s1)> {> > // Compares 5 characters from 0 index of s1 with 'Geeks'> > if> ((s1.compare(0, 5, 'Geeks')) == 0)> > cout < < s1 < < ' are ' < < 'awesome people';> > > else> > cout < < 'Strings didn't match ';> > }> // Driver Code> int> main()> {> > string s1('Geeks');> > compareOperation(s1);> > > return> 0;> }>

Produktion:

Geeks are awesome people 

Syntaks 6: Sammenligner højst len-tegn af streng *this, startende med index idx med chars_len-tegn i tegnarray-tegnene.

 int string::compare (size_type idx, size_type len, const char* chars,  size_type chars_len)const 

Bemærk, at tegn skal have mindst chars_len-tegn. Tegnene kan have vilkårlige værdier. Derfor har ' ' ingen særlig betydning.

CPP

// CPP code to demonstrate> // int string::compare (size_type idx, size_type len,> // const char* chars, size_type chars_len)const> #include> using> namespace> std;> void> compareOperation(string s1, string s2)> {> > // Compares 5 characters from 0 index of s1 with> > // 5 characters of string 'Geeks'> > if> ((s1.compare(0, 5, 'Geeks', 5)) == 0)> > cout < < 'This is ' < < s1 < < s2 ;> > > else> > cout < < 'Strings didn't match ';> }> // Driver Code> int> main()> {> > string s1('Geeks');> > string s2('forGeeks');> > compareOperation(s1, s2);> > > return> 0;> }>