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count_if(): A unary predicate that determines if number is divisible by 3
#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
bool dividesBy3(int i)
{
if((i%3) == 0) return true;
return false;
}
int main()
{
vector<int> v;
int i;
for(i=1; i < 20; i++) v.push_back(i);
for(i=0; i<v.size(); i++)
cout << v[i] << endl;
i = count_if(v.begin(), v.end(), dividesBy3);
cout << i << " numbers are divisible by 3.\n";
return 0;
}Use std::count_if to count number of elements in vector that are greater than 9
#include <iostream>
using std::cout;
using std::endl;
#include <algorithm>
#include <numeric>
#include <vector>
#include <iterator>
bool greater9( int );
int main()
{
std::ostream_iterator< int > output( cout, " " );
int a2[ 10 ] = { 100, 2, 8, 1, 50, 3, 8, 8, 9, 10 };
std::vector< int > v2( a2, a2 + 10 ); // copy of a2
cout << "\n\nVector v2 contains: ";
std::copy( v2.begin(), v2.end(), output );
// count number of elements in v2 that are greater than 9
int result = std::count_if( v2.begin(), v2.end(), greater9 );
cout << "\nNumber of elements greater than 9: " << result;
cout << endl;
return 0;
}
bool greater9( int value )
{
return value > 9;
}Vector v2 contains: 100 2 8 1 50 3 8 8 9 10
Number of elements greater than 9: 3
