How to count the Number of Occurrences of Specific Item in the Vector in C++

How to count the Number of Occurrences of Specific Item in the Vector in C++ ?

Answer

To count the number of occurrences of a specific item in a vector in C++, you can use the std::count function from the <algorithm> library.


✐ Examples

1 Count Number of Occurrences of a Specific Number in a Numeric Vector

In this example,

  1. We include the necessary headers <iostream> for input and output and <vector> for using the vector container, and <algorithm> for the std::count function.
  2. We use the std namespace to simplify code.
  3. We create a vector named vec with a set of numerical values using the std::vector<int> container.
  4. We define a variable item that holds the value we want to count in the vector.
  5. We use the std::count function to count the occurrences of item in vec. The function takes two iterators to specify the range of elements to examine and the value to count.
  6. Finally, we print the result to standard output using the std::cout stream.

C++ Program

#include &lt;iostream&gt;
#include &lt;vector&gt;
#include &lt;algorithm&gt;

int main() {
    std::vector&lt;int&gt; vec = {1, 2, 3, 2, 2, 4, 5, 2};
    int item = 2;
    int count = std::count(vec.begin(), vec.end(), item);
    std::cout &lt;&lt; count &lt;&lt; std::endl;
    return 0;
}

Output

4

2 Count Number of Occurrences of a Specific String in a Character Vector

In this example,

  1. We include the necessary headers <iostream> for input and output, <vector> for using the vector container, and <algorithm> for the std::count function.
  2. We use the std namespace to simplify code.
  3. We create a vector named char_vec with a set of string values using the std::vector<std::string> container.
  4. We define a variable str_item that holds the string we want to count in the vector.
  5. We use the std::count function to count the occurrences of str_item in char_vec. The function takes two iterators to specify the range of elements to examine and the value to count.
  6. Finally, we print the result to standard output using the std::cout stream.

C++ Program

#include &lt;iostream&gt;
#include &lt;vector&gt;
#include &lt;algorithm&gt;
#include &lt;string&gt;

int main() {
    std::vector&lt;std::string&gt; char_vec = {"apple", "banana", "apple", "cherry", "banana", "apple"};
    std::string str_item = "apple";
    int count = std::count(char_vec.begin(), char_vec.end(), str_item);
    std::cout &lt;&lt; count &lt;&lt; std::endl;
    return 0;
}

Output

3

3 Count Number of Occurrences of a Specific Boolean Value in a Boolean Vector

In this example,

  1. We include the necessary headers <iostream> for input and output and <vector> for using the vector container, and <algorithm> for the std::count function.
  2. We use the std namespace to simplify code.
  3. We create a vector named bool_vec with a set of boolean values using the std::vector<bool> container.
  4. We define a variable bool_item that holds the boolean value we want to count in the vector.
  5. We use the std::count function to count the occurrences of bool_item in bool_vec. The function takes two iterators to specify the range of elements to examine and the value to count.
  6. Finally, we print the result to standard output using the std::cout stream.

C++ Program

#include &lt;iostream&gt;
#include &lt;vector&gt;
#include &lt;algorithm&gt;

int main() {
    std::vector&lt;bool&gt; bool_vec = {true, false, true, true, false, true, false};
    bool bool_item = true;
    int count = std::count(bool_vec.begin(), bool_vec.end(), bool_item);
    std::cout &lt;&lt; count &lt;&lt; std::endl;
    return 0;
}

Output

4

Summary

In this tutorial, we learned How to count the Number of Occurrences of Specific Item in the Vector in C++ language with well detailed examples.


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