C++ Tutorial/map multimap/map — различия между версиями
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Текущая версия на 10:28, 25 мая 2010
Содержание
- 1 A phone list in which a person"s name is the key and the phone number is the value.
- 2 Computing an inner product of tuples represented as maps
- 3 Create string float map
- 4 Declare a char int map
- 5 Define string-string map and loop through the value key-pair
- 6 Demonstrating an STL map
- 7 Multiple map
- 8 Store objects in a map
- 9 Use string as the key and value in a map
A phone list in which a person"s name is the key and the phone number is the value.
#include <iostream>
#include <string>
#include <map>
#include <utility>
using namespace std;
void show(const char *msg, map<string, string> mp);
int main() {
map<string, string> phonemap;
phonemap["A"] = "444-555-1234";
phonemap["B"] = "555-555-6576";
phonemap["C"] = "555-555-9843";
show("Here is the original map: ", phonemap);
return 0;
}
// Display the contents of a map<string, string> by using an iterator.
void show(const char *msg, map<string, string> mp) {
map<string, string>::iterator itr;
cout << msg << endl;
for(itr=mp.begin(); itr != mp.end(); ++itr)
cout << " " << itr->first << ": " << itr->second << endl;
cout << endl;
}Computing an inner product of tuples represented as maps
#include <map>
#include <iostream>
using namespace std;
int main()
{
const long N = 600000; // Length of tuples x and y
const long S = 10; // Sparseness factor
map<long, double> x, y;
for (long k = 0; 3 * k * S < N; ++k)
x[3 * k * S] = 1.0;
for (long k = 0; 5 * k * S < N; ++k)
y[5 * k * S] = 1.0;
double sum;
map<long, double>::iterator ix, iy;
for (sum = 0.0, ix = x.begin(); ix != x.end(); ++ix) {
long i = ix->first;
iy = y.find(i);
if (iy != y.end())
sum += ix->second * iy->second;
}
cout << sum << endl;
return 0;
}4000
Create string float map
/* 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 <map>
#include <string>
using namespace std;
int main()
{
/* type of the container:
* - map: elements key/value pairs
* - string: keys have type string
* - float: values have type float
*/
typedef map<string,float> StringFloatMap;
StringFloatMap coll;
// insert some elements into the collection
coll["VAT"] = 0.15;
coll["Pi"] = 3.1415;
coll["an arbitrary number"] = 4983.223;
coll["Null"] = 0;
/* print all elements
* - iterate over all elements
* - element member first is the key
* - element member second is the value
*/
StringFloatMap::iterator pos;
for (pos = coll.begin(); pos != coll.end(); ++pos) {
cout << "key: \"" << pos->first << "\" "
<< "value: " << pos->second << endl;
}
}key: "Null" value: 0 key: "Pi" value: 3.1415 key: "VAT" value: 0.15 key: "an arbitrary number" value: 4983.22
Declare a char int map
#include <iostream>
#include <map>
using namespace std;
int main()
{
map<char, int> m;
// put pairs into map
for(int i=0; i<26; i++) {
m.insert(pair<char, int>("A"+i, 65+i));
}
char ch = "G";
map<char, int>::iterator p;
// find value given key
p = m.find(ch);
if(p != m.end())
cout << "Its ASCII value is " << p->second;
else
cout << "Key not in map.\n";
return 0;
}Its ASCII value is 71
Define string-string map and loop through the value key-pair
#include <iostream>
#include <map>
#include <string>
using namespace std;
int main( ) {
map<string, string> strMap;
strMap["Monday"] = "1";
strMap["Tuesday"] = "2";
strMap["Wednesday"] = "3";
strMap["Thursday"] = "4";
strMap["Friday"] = "5";
strMap["Saturday"] = "6";
strMap.insert(pair<string, string>("Sunday", "7"));
for (map<string, string>::iterator p = strMap.begin( );
p != strMap.end( ); ++p ) {
cout << "English: " << p->first<< ", #: " << p->second << endl;
}
cout << endl;
}English: Friday, #: 5 English: Monday, #: 1 English: Saturday, #: 6 English: Sunday, #: 7 English: Thursday, #: 4 English: Tuesday, #: 2 English: Wednesday, #: 3
Demonstrating an STL map
#include <iostream>
#include <map>
#include <string>
using namespace std;
int main()
{
map<string, long> directory;
directory["A"] = 1234567;
directory["B"] = 9876543;
directory["C"] = 3459876;
string name = "A";
if (directory.find(name) != directory.end())
cout << "The phone number for " << name
<< " is " << directory[name] << "\n";
else
cout << "Sorry, no listing for " << name << "\n";
return 0;
}The phone number for A is 1234567
Multiple map
/* 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 <map>
#include <string>
#include <iomanip>
using namespace std;
int main()
{
// define multimap type as string/string dictionary
typedef multimap<string,string> StrStrMMap;
// create empty dictionary
StrStrMMap dict;
// insert some elements in random order
dict.insert(make_pair("day","Tag"));
dict.insert(make_pair("strange","fremd"));
dict.insert(make_pair("car","Auto"));
dict.insert(make_pair("smart","elegant"));
dict.insert(make_pair("trait","Merkmal"));
dict.insert(make_pair("strange","seltsam"));
dict.insert(make_pair("smart","raffiniert"));
dict.insert(make_pair("smart","klug"));
dict.insert(make_pair("clever","raffiniert"));
// print all elements
StrStrMMap::iterator pos;
cout.setf (ios::left, ios::adjustfield);
cout << " " << setw(10) << "english "
<< "german " << endl;
cout << setfill("-") << setw(20) << ""
<< setfill(" ") << endl;
for (pos = dict.begin(); pos != dict.end(); ++pos) {
cout << " " << setw(10) << pos->first.c_str()
<< pos->second << endl;
}
cout << endl;
// print all values for key "smart"
string word("smart");
cout << word << ": " << endl;
for (pos = dict.lower_bound(word);
pos != dict.upper_bound(word); ++pos) {
cout << " " << pos->second << endl;
}
// print all keys for value "raffiniert"
word = ("raffiniert");
cout << word << ": " << endl;
for (pos = dict.begin(); pos != dict.end(); ++pos) {
if (pos->second == word) {
cout << " " << pos->first << endl;
}
}
}english german
--------------------
car Auto
clever raffiniert
day Tag
smart elegant
smart raffiniert
smart klug
strange fremd
strange seltsam
trait Merkmal
smart:
elegant
raffiniert
klug
raffiniert:
clever
smart
Store objects in a map
#include <iostream>
#include <map>
#include <cstring>
using namespace std;
class Name {
char str[40];
public:
Name() {
strcpy(str, "");
}
Name(char *s) {
strcpy(str, s);
}
char *get() {
return str;
}
};
// Must define less than relative to Name objects.
bool operator<(Name a, Name b)
{
return strcmp(a.get(), b.get()) < 0;
}
class Number {
char str[80];
public:
Number() {
strcmp(str, "");
}
Number(char *s) {
strcpy(str, s);
}
char *get() {
return str;
}
};
int main()
{
map<Name, Number> directory;
directory.insert(pair<Name, Number>(Name("T"),Number("555-4444")));
directory.insert(pair<Name, Number>(Name("C"),Number("555-3333")));
directory.insert(pair<Name, Number>(Name("J"),Number("555-2222")));
directory.insert(pair<Name, Number>(Name("R"),Number("555-1111")));
char str[80] = "T";
map<Name, Number>::iterator p;
p = directory.find(Name(str));
if(p != directory.end())
cout << "Phone number: " << p->second.get();
else
cout << "Name not in directory.\n";
return 0;
}Phone number: 555-4444
Use string as the key and value in a map
#include <iostream>
#include <map>
#include <string>
using namespace std;
int main()
{
map<string, string> directory;
directory.insert(pair<string, string>("T", "555-4444"));
directory.insert(pair<string, string>("C", "555-3333"));
directory.insert(pair<string, string>("J", "555-2222"));
directory.insert(pair<string, string>("R", "555-1111"));
string s = "T";
map<string, string>::iterator p;
p = directory.find(s);
if(p != directory.end())
cout << "Phone number: " << p->second;
else
cout << "Name not in directory.\n";
return 0;
}Phone number: 555-4444
