Define == operator in order to use the find method
#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
using namespace std;
class Employee {
string name;
unsigned number;
public:
Employee() { name = ""; number = 0; }
Employee(string n, unsigned num) {
name = n;
number = num;
}
string get_name() { return name; }
unsigned get_number() { return number; }
};
void show(vector<Employee> vect) {
vector<Employee>::iterator itr;
for(itr=vect.begin(); itr != vect.end(); ++itr)
cout << itr->get_number() << " " << itr->get_name() << endl;;
}
bool operator==(Employee a, Employee b){
return a.get_number() == b.get_number();
}
int main()
{
vector<Employee> employeeList;
employeeList.push_back(Employee("A", 9));
employeeList.push_back(Employee("B", 8));
employeeList.push_back(Employee("C", 6));
employeeList.push_back(Employee("D", 1));
show(employeeList);
vector<Employee>::iterator itr;
itr = find(employeeList.begin(), employeeList.end(), Employee("", 2));
cout << itr->get_name();
return 0;
}Demonstrating generic find algorithm with an array
#include <iostream>
#include <cassert>
#include <algorithm> // for find
using namespace std;
int main()
{
char s[] = "C++ is a better C";
int len = strlen(s);
// Search for the first occurrence of the letter e:
const char* where = find(&s[0], &s[len], "e");
cout << *where<< endl;
where = find(&s[0], &s[len], "A");
cout << *where<< endl;
return 0;
}e
Find an Element and Its Position in a Vector
#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
int main ()
{
vector <int> v;
v.push_back (50);
v.push_back (2991);
v.push_back (23);
v.push_back (9999);
vector <int>::iterator i = v.begin ();
while (i != v.end ()){
cout << *i << endl;
++ i;
}
i = find (v.begin (),v.end (), 2991);
if (i != v.end ())
{
int nPosition = distance (v.begin (), i);
cout << "Value "<< *i;
cout << " found in the vector at position: " << nPosition << endl;
}
return 0;
}find an element in a list
//erase an element in a list
//Combine erase and remove to remove a found element
#include <iostream>
#include <string>
#include <list>
#include <algorithm>
#include <functional>
using namespace std;
int main( ) {
list<string> lstStr;
lstStr.push_back("A");
lstStr.push_back("B");
lstStr.push_back("C");
lstStr.push_back("D");
lstStr.push_back("E");
list<string>::iterator p;
p = find(lstStr.begin( ), lstStr.end( ), "C");
p = lstStr.erase(p);
lstStr.erase(remove(lstStr.begin( ), lstStr.end( ), "D"),lstStr.end( ));
}find a value in vector
#include <algorithm>
#include <vector>
#include <iostream>
using namespace std;
int main(int argc, char** argv)
{
int num = 4;
vector<int> myVector;
myVector.push_back(1);
myVector.push_back(2);
myVector.push_back(3);
myVector.push_back(4);
vector<int>::iterator it = find(myVector.begin(), myVector.end(), num);
if (it == myVector.end()) {
cout << "Could not find " << num << endl;
} else {
cout << "Found " << *it << endl;
}
return (0);
}Find empty string
#include <functional>
#include <algorithm>
#include <string>
#include <vector>
#include <iostream>
using namespace std;
void findEmptyString(const vector<string>& strings)
{
vector<string>::const_iterator it = find_if(strings.begin(), strings.end(),mem_fun_ref(&string::empty));
if (it == strings.end()) {
cout << "No empty strings!\n";
} else {
cout << "Empty string at position: " << it - strings.begin() << endl;
}
}
int main(int argc, char** argv)
{
vector<string> myVector;
string one = "blah";
string two = "";
myVector.push_back(one);
myVector.push_back(one);
myVector.push_back(two);
myVector.push_back(one);
findEmptyString(myVector);
return (0);
}Find the maximum element in a range in a list
/* 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 <list>
#include <algorithm>
using namespace std;
int main()
{
list<int> coll;
list<int>::iterator pos;
// insert elements from 20 to 40
for (int i=20; i<=40; ++i) {
coll.push_back(i);
}
/* find position of element with value 3
* - there is none, so pos gets coll.end()
*/
pos = find (coll.begin(), coll.end(), // range
3); // value
/* reverse the order of elements between found element and the end
* - because pos is coll.end() it reverses an empty range
*/
reverse (pos, coll.end());
// find positions of values 25 and 35
list<int>::iterator pos25, pos35;
pos25 = find (coll.begin(), coll.end(), // range
25); // value
pos35 = find (coll.begin(), coll.end(), // range
35); // value
/* print the maximum of the corresponding range
* - note: including pos25 but excluding pos35
*/
cout << "max: " << *max_element (pos25, pos35) << endl;
// process the elements including the last position
cout << "max: " << *max_element (pos25, ++pos35) << endl;
}max: 34
max: 35
Generic find algorithm: use find function to find an element in an array
#include <iostream>
#include <cassert>
#include <algorithm>
#include <list>
#include <iterator>
using namespace std;
int main()
{
int a[10] = {12, 3, 25, 7, 11, 213, 7, 123, 29, -31};
// Find the first element equal to 7 in the array:
int* ptr = find(&a[0], &a[10], 7);
assert (*ptr == 7 && *(ptr+1) == 11);
cout << *ptr;
return 0;
}7"
Generic find algorithm with input iterators associated with io streams
#include <iostream>
#include <cassert>
#include <algorithm>
#include <list>
#include <iterator>
using namespace std;
int main()
{
cout << "Type some characters, including an "x" followed\n"
<< "by at least one nonwhite-space character: " << flush;
istream_iterator<char> in(cin);
istream_iterator<char> eos;
find(in, eos, "x");
cout << "The first nonwhite-space character following\n"
<< "the first "x" was "" << *(++in) << ""." << endl;
return 0;
}Type some characters, including an "x" followed
by at least one nonwhite-space character: x is before y
The first nonwhite-space character following
the first "x" was "i".
Locate first occurrence of a value in a vector
#include <iostream>
using std::cout;
using std::endl;
#include <algorithm>
#include <vector>
#include <iterator>
int main()
{
int a[ 10 ] = { 10, 2, 17, 5, 16, 8, 13, 11, 20, 7 };
std::vector< int > v( a, a + 10 ); // copy of a
std::ostream_iterator< int > output( cout, " " );
cout << "Vector v contains: ";
std::copy( v.begin(), v.end(), output ); // display output vector
std::vector< int >::iterator location;
location = std::find( v.begin(), v.end(), 16 );
if ( location != v.end() ) // found 16
cout << "\n\nFound 16 at location " << ( location - v.begin() );
else // 16 not found
cout << "\n\n16 not found";
cout << endl;
return 0;
}Vector v contains: 10 2 17 5 16 8 13 11 20 7
Found 16 at location 4
Use assert to check the find method
#include <iostream>
#include <cassert>
#include <algorithm>
#include <list>
#include <iterator>
using namespace std;
int main()
{
int a[10] = {12, 3, 25, 7, 11, 213, 7, 123, 29, -31};
// Find the first element equal to 7 in the array:
int* ptr = find(&a[0], &a[10], 7);
assert (*ptr == 7 && *(ptr+1) == 11);
cout << *ptr;
return 0;
}7
Use find algorithm to find an element in a list
#include <iostream>
#include <cassert>
#include <algorithm>
#include <list>
#include <iterator>
using namespace std;
int main()
{
int a[10] = {12, 3, 25, 7, 11, 213, 7, 123, 29, -31};
list<int> list1(&a[0], &a[10]);
// Find the first element equal to 7 in list1:
list<int>::iterator i = find(list1.begin(),list1.end(),7);
assert (*i == 7 && *(++i) == 11);
cout << *i;
return 0;
}11"
Use find to search an element in a container
/* 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 <vector>
#include <deque>
#include <list>
#include <set>
#include <map>
#include <string>
#include <algorithm>
#include <iterator>
#include <functional>
#include <numeric>
/* PRINT_ELEMENTS()
* - prints optional C-string optcstr followed by
* - all elements of the collection coll
* - separated by spaces
*/
template <class T>
inline void PRINT_ELEMENTS (const T& coll, const char* optcstr="")
{
typename T::const_iterator pos;
std::cout << optcstr;
for (pos=coll.begin(); pos!=coll.end(); ++pos) {
std::cout << *pos << " ";
}
std::cout << std::endl;
}
/* INSERT_ELEMENTS (collection, first, last)
* - fill values from first to last into the collection
* - NOTE: NO half-open range
*/
template <class T>
inline void INSERT_ELEMENTS (T& coll, int first, int last)
{
for (int i=first; i<=last; ++i) {
coll.insert(coll.end(),i);
}
}
using namespace std;
int main()
{
list<int> coll;
INSERT_ELEMENTS(coll,1,9);
INSERT_ELEMENTS(coll,1,9);
PRINT_ELEMENTS(coll,"coll: ");
// find first element with value 4
list<int>::iterator pos1;
pos1 = find (coll.begin(), coll.end(), // range
4); // value
/* find second element with value 4
* - note: continue the search behind the first 4 (if any)
*/
list<int>::iterator pos2;
if (pos1 != coll.end()) {
pos2 = find (++pos1, coll.end(), // range
4); // value
}
/* print all elements from first to second 4 (both included)
* - note: now we need the position of the first 4 again (if any)
* - note: we have to pass the position behind the second 4 (if any)
*/
if (pos1!=coll.end() && pos2!=coll.end()) {
copy (--pos1, ++pos2,
ostream_iterator<int>(cout," "));
cout << endl;
}
}coll: 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9
4 5 6 7 8 9 1 2 3 4
Use istream_iterator and find
#include <iostream>
#include <cassert>
#include <algorithm>
#include <list>
#include <iterator>
using namespace std;
int main()
{
cout << "Type some characters, including an "x" followed\n"
<< "by at least one nonwhite-space character: " << flush;
istream_iterator<char> in(cin);
istream_iterator<char> eos;
find(in, eos, "x");
cout << "The first nonwhite-space character following\n"
<< "the first "x" was "" << *(++in) << ""." << endl;
return 0;
}Type some characters, including an "x" followed
by at least one nonwhite-space character: x is after y
The first nonwhite-space character following
the first "x" was "i".
Using find with normal iteration
#include <iostream>
#include <vector>
#include <algorithm> // for find
#include <iterator>
using namespace std;
int main()
{
string s("It is him.");
vector<char> vector1(s.begin(), s.end());
ostream_iterator<char> out(cout, " ");
vector<char>::iterator i = find(vector1.begin(), vector1.end(), "i");
cout << "chars from the first i to the end: ";
copy(i, vector1.end(), out); cout << endl;
return 0;
}chars from the first i to the end: i s h i m .
