You should have a knowledge of vectors and vector iterators.
What does the count() algorithm do?
It counts the # of a specified value within a vector
The syntax for the count() algorithm:
int count = count(<where to begin searching>, <where to stop searching>, <value to search for>);
What to include:
cpp
#include <iostream> // just to output what's going on
#include <algorithm> // algorithms!
#include <vector> // vector to use algorithms on
using namespace std;
Next, we need to begin our int main () function. I'm gonna assume you know how to do this, and move on.
We need to declare a vector and a vector iterator:
cpp
vector <int> myVec; // create a vector called myVec
vector <int> :: iterator it; // create a vector iterator called it
We now need a loop to fill our vector with some values. Let's use some random numbers:
cpp
for (int i = 0; i < 9; ++i)
{
int random = rand () % 5; // generate a random number
myVec.push_back(random); // fill the vector with some values
}
Let's print the contents:
cpp
cout << "Contents: ";
for (it = myVec.begin(); it != myVec.end(); ++it)
cout << *it << " "; // print the contents of myVec
Next is the count function. Ready? (Take a look at the syntax at the beginning of this tutorial to compare them)
cpp
int count_value = count (myVec.begin(), myVec.end(), 4);
Now all we need to do is print our count variable and exit the program:
cpp
cout << endl << "Number of 4s stored in vector: " << count_value;
cin.get (); // pause
return EXIT_SUCCESS; // everything went OK
For those of you who learn better by example, here is the complete code:
cpp
#include <iostream> // just to output what's going on
#include <algorithm> // algorithms!
#include <vector> // vector to use algorithms on
using namespace std;
int main ()
{
vector <int> myVec; // create a vector called myVec
vector <int> :: iterator it; // create a vector iterator called it
for (int i = 0; i < 9; ++i)
{
int random = rand () % 5; // generate a random number
myVec.push_back(random); // fill the vector with some values
}
cout << "Contents: ";
for (it = myVec.begin(); it != myVec.end(); ++it)
cout << *it << " "; // print the contents of myVec
int count_value = count (myVec.begin(), myVec.end(), 4);
cout << endl << "Number of 4s stored in vector: " << count_value;
cin.get (); // pause
return EXIT_SUCCESS; // everything went OK
}