C++ Tutorial/map multimap/map compare
Содержание
Compare two maps
<source lang="cpp">#include <iostream>
- include <string>
- include <map>
using namespace std; void show(const char *msg, map<string, int> mp); int main() {
map<string, int> m;
m.insert(pair<string, int>("A", 100));
m.insert(pair<string, int>("G", 300));
m.insert(pair<string, int>("B", 200));
// Create another map that is the same as the first.
map<string, int> m2(m);
show("Contents of m2: ", m2);
// Compare two maps.
if(m == m2) cout << "m and m2 are equivalent.\n\n";
return 0;
} // Display the contents of a map<string, int> by using an iterator. void show(const char *msg, map<string, int> mp) {
map<string, int>::iterator itr; cout << msg << endl; for(itr=mp.begin(); itr != mp.end(); ++itr) cout << " " << itr->first << ", " << itr->second << endl; cout << endl;
}</source>
Create another map that is the same as the first
<source lang="cpp">#include <iostream>
- include <string>
- include <map>
using namespace std; void show(const char *msg, map<string, int> mp); int main() {
map<string, int> m;
m.insert(pair<string, int>("A", 100));
m.insert(pair<string, int>("G", 300));
m.insert(pair<string, int>("B", 200));
map<string, int>::iterator itr;
// Create another map that is the same as the first.
map<string, int> m2(m);
show("Contents of m2: ", m2);
return 0;
} // Display the contents of a map<string, int> by using an iterator. void show(const char *msg, map<string, int> mp) {
map<string, int>::iterator itr; cout << msg << endl; for(itr=mp.begin(); itr != mp.end(); ++itr) cout << " " << itr->first << ", " << itr->second << endl; cout << endl;
}</source>
Determine the lexicographical relationship between two maps
<source lang="cpp">#include <iostream>
- include <string>
- include <map>
using namespace std; void show(const char *msg, map<string, int> mp); int main() {
map<string, int> m;
m.insert(pair<string, int>("A", 100));
m.insert(pair<string, int>("G", 300));
m.insert(pair<string, int>("B", 200));
// Declare an iterator to a map<string, int>.
map<string, int>::iterator itr;
// Create another map that is the same as the first.
map<string, int> m2(m);
show("Contents of m2: ", m2);
if(m < m2) cout << "m is less than m2." << endl;
// Remove the Beta from m.
m.erase("Beta");
show("m after removing Beta: ", m);
if(m > m2)
cout << "Now, m is greater than m2." << endl;
return 0;
} // Display the contents of a map<string, int> by using an iterator. void show(const char *msg, map<string, int> mp) {
map<string, int>::iterator itr; cout << msg << endl; for(itr=mp.begin(); itr != mp.end(); ++itr) cout << " " << itr->first << ", " << itr->second << endl; cout << endl;
}</source>
Map comparison
<source lang="cpp">/* The following code example is taken from the book
* "The C++ Standard Library - A Tutorial and Reference" * by Nicolai M. Josuttis, Addison-Wesley, 1999 * * (C) Copyright Nicolai M. Josuttis 1999. * Permission to copy, use, modify, sell and distribute this software * is granted provided this copyright notice appears in all copies. * This software is provided "as is" without express or implied * warranty, and with no claim as to its suitability for any purpose. */
- include <iostream>
- include <iomanip>
- include <map>
- include <string>
- include <algorithm>
using namespace std; /* function object to compare strings
* - allows you to set the comparison criterion at runtime * - allows you to compare case insensitive */
class RuntimeStringCmp {
public:
// constants for the comparison criterion
enum cmp_mode {normal, nocase};
private:
// actual comparison mode
const cmp_mode mode;
// auxiliary function to compare case insensitive
static bool nocase_compare (char c1, char c2)
{
return toupper(c1) < toupper(c2);
}
public:
// constructor: initializes the comparison criterion
RuntimeStringCmp (cmp_mode m=normal) : mode(m) {
}
// the comparison
bool operator() (const string& s1, const string& s2) const {
if (mode == normal) {
return s1<s2;
}
else {
return lexicographical_compare (s1.begin(), s1.end(),
s2.begin(), s2.end(),
nocase_compare);
}
}
}; /* container type:
* - map with * - string keys * - string values * - the special comparison object type */
typedef map<string,string,RuntimeStringCmp> StringStringMap; // function that fills and prints such containers void fillAndPrint(StringStringMap& coll); int main() {
// create a container with the default comparison criterion StringStringMap coll1; fillAndPrint(coll1); // create an object for case-insensitive comparisons RuntimeStringCmp ignorecase(RuntimeStringCmp::nocase); // create a container with the case-insensitive comparisons criterion StringStringMap coll2(ignorecase); fillAndPrint(coll2);
} void fillAndPrint(StringStringMap& coll) {
// fill insert elements in random order
coll["Deutschland"] = "Germany";
coll["deutsch"] = "German";
coll["Haken"] = "snag";
coll["arbeiten"] = "work";
coll["Hund"] = "dog";
coll["gehen"] = "go";
coll["Unternehmen"] = "enterprise";
coll["unternehmen"] = "undertake";
coll["gehen"] = "walk";
coll["Bestatter"] = "undertaker";
// print elements
StringStringMap::iterator pos;
cout.setf(ios::left, ios::adjustfield);
for (pos=coll.begin(); pos!=coll.end(); ++pos) {
cout << setw(15) << pos->first.c_str() << " "
<< pos->second << endl;
}
cout << endl;
}</source>
Bestatter undertaker Deutschland Germany Haken snag Hund dog Unternehmen enterprise arbeiten work deutsch German gehen walk unternehmen undertake arbeiten work Bestatter undertaker deutsch German Deutschland Germany gehen walk Haken snag Hund dog Unternehmen undertake
Map with comparator(functor)
<source lang="cpp">#include <iostream>
- include <map>
- include <string>
using namespace std; class Employee {
friend class EmployeeLessThan;
public:
Employee(const string& first, const string& last) : lastName_(last), firstName_(first) {}
string getFirstName( ) const {return(firstName_);}
string getLastName( ) const {return(lastName_);}
private:
string lastName_; string firstName_;
}; class EmployeeLessThan { public:
bool operator( )(const Employee& emp1, const Employee& emp2) const {
if (emp1.lastName_ < emp2.lastName_)
return(true);
else if (emp1.lastName_ == emp2.lastName_)
return(emp1.firstName_ < emp2.firstName_);
else
return(false);
}
}; int main( ) {
map<Employee, string, EmployeeLessThan> empMap;
Employee emp1("B", "A"),emp2("J", "G"),emp3("F", "S"),emp4("G", "G");
empMap[emp1] = "tester";
empMap[emp2] = "coder";
empMap[emp3] = "programmer";
empMap[emp4] = "developer";
for (map<Employee, string, EmployeeLessThan>::const_iterator p =
empMap.begin( ); p != empMap.end( ); ++p) {
cout << p->first.getFirstName( ) << " " << p->first.getLastName( ) << " is " << p->second << endl;
}
}</source>
B A is tester G G is developer J G is coder F S is programmer
