Demonstrate the find() and find_if() algorithms.
#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
using namespace std;
bool is_short_str(string str);
int main()
{
vector<string> v;
vector<string>::iterator itr;
v.push_back("one");
v.push_back("two");
v.push_back("three");
v.push_back("four");
v.push_back("five");
v.push_back("six");
for(unsigned i=0; i < v.size(); ++i)
cout << v[i] << " ";
itr = find(v.begin(), v.end(), "two");
if(itr != v.end()) {
cout << "Replacing with \"TWO\"" << endl;
*itr = "TWO";
}
return 0;
}
// Return true if the string is 3 characters or less.
bool is_short_str(string str)
{
if(str.size() <= 3) return true;
return false;
}#include <iostream>
#include <vector>
#include <algorithm>
#include <cstring>
#include <cctype>
using namespace std;
bool is_sentence_start(char ch);
template<class InIter>
void show_range(const char *msg, InIter start, InIter end);
int main()
{
vector<char> v;
vector<char>::iterator itr;
const char *str = "this is a test";
for(unsigned i=0; i < strlen(str); i++)
v.push_back(str[i]);
show_range("Contents of v: ", v.begin(), v.end());
cout << endl;
vector<char>::iterator itr_start, itr_end;
itr_start = v.begin();
do {
itr_start = find_if(itr_start, v.end(), is_sentence_start);
itr_end = find_if(itr_start, v.end(), is_sentence_start);
show_range("", itr_start, itr_end);
} while(itr_end != v.end());
return 0;
}
// Return true if ch is the first letter in a sentence.
bool is_sentence_start(char ch) {
static bool endofsentence = true;
if(isalpha(ch) && endofsentence ) {
endofsentence = false;
return true;
}
if(ch=="." || ch=="?" || ch=="!") endofsentence = true;
return false;
}
template<class InIter>
void show_range(const char *msg, InIter start, InIter end) {
InIter itr;
cout << msg << endl;
for(itr = start; itr != end; ++itr)
cout << *itr;
cout << endl;
}Find value in a vector with find_if
#include <algorithm>
#include <vector>
#include <iostream>
using namespace std;
bool perfectScore(int num)
{
return (num >= 100);
}
int main(int argc, char** argv){
int num;
vector<int> myVector;
myVector.push_back(1);
myVector.push_back(2);
myVector.push_back(3);
myVector.push_back(4);
vector<int>::iterator it = find_if(myVector.begin(), myVector.end(),perfectScore);
if (it == myVector.end()) {
cout << "No perfect scores\n";
} else {
cout << "Found a \"perfect\" score of " << *it << endl;
}
return (0);
}map: find_if
/* 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 <algorithm>
#include <map>
using namespace std;
/* function object to check the value of a map element
*/
template <class K, class V>
class value_equals {
private:
V value;
public:
// constructor (initialize value to compare with)
value_equals (const V& v)
: value(v) {
}
// comparison
bool operator() (pair<const K, V> elem) {
return elem.second == value;
}
};
int main()
{
typedef map<float,float> FloatFloatMap;
FloatFloatMap coll;
FloatFloatMap::iterator pos;
// fill container
coll[1]=7;
coll[2]=4;
coll[3]=2;
coll[4]=3;
coll[5]=6;
coll[6]=1;
coll[7]=3;
// search an element with value 3.0
pos = find_if(coll.begin(),coll.end(), // linear complexity
value_equals<float,float>(3.0));
if (pos != coll.end()) {
cout << pos->first << ": "
<< pos->second << endl;
}
}4: 3
std::find_if with predicate
#include <iostream>
using std::cout;
using std::endl;
#include <algorithm>
#include <vector>
#include <iterator>
bool greater10( int value );
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
// locate first occurrence of 16 in v
std::vector< int >::iterator location;
// locate first occurrence of value greater than 10 in v
location = std::find_if( v.begin(), v.end(), greater10 );
if ( location != v.end() ) // found value greater than 10
cout << "\n\nThe first value greater than 10 is " << *location
<< "\nfound at location " << ( location - v.begin() );
else // value greater than 10 not found
cout << "\n\nNo values greater than 10 were found";
cout << endl;
return 0;
}
bool greater10( int value )
{
return value > 10;
}Vector v contains: 10 2 17 5 16 8 13 11 20 7
The first value greater than 10 is 17
found at location 2
Use find_if to find first element divisible by 3
/* 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()
{
vector<int> coll;
vector<int>::iterator pos;
INSERT_ELEMENTS(coll,1,9);
PRINT_ELEMENTS(coll,"coll: ");
// find first element divisible by 3
pos = find_if (coll.begin(), coll.end(),
not1(bind2nd(modulus<int>(),3)));
// print its position
cout << "the "
<< distance(coll.begin(),pos) + 1
<< ". element is the first divisible by 3" << endl;
}coll: 1 2 3 4 5 6 7 8 9
the 3. element is the first divisible by 3
Use find_if to find first element greater than 3
/* 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()
{
vector<int> coll;
vector<int>::iterator pos;
INSERT_ELEMENTS(coll,1,9);
PRINT_ELEMENTS(coll,"coll: ");
// find first element greater than 3
pos = find_if (coll.begin(), coll.end(), // range
bind2nd(greater<int>(),3)); // criterion
// print its position
cout << "the "
<< distance(coll.begin(),pos) + 1
<< ". element is the first greater than 3" << endl;
}coll: 1 2 3 4 5 6 7 8 9
the 4. element is the first greater than 3
