# std::count() in C++ STL

• Difficulty Level : Easy
• Last Updated : 22 Sep, 2019

std::count() returns number of occurrences of an element in a given range. Returns the number of elements in the range [first,last) that compare equal to val.

// Returns count of occurrences of value in
// range [begin, end]
int count(Iterator first, Iterator last, T &val)

first, last : Input iterators to the initial and final positions of the sequence of elements.
val : Value to match

Complexity It’s order of complexity O(n). Compares once each element with the particular value.

Counting occurrences in an array.

 `// C++ program for count in C++ STL for``// array``#include ``using` `namespace` `std;`` ` `int` `main()``{``    ``int` `arr[] = { 3, 2, 1, 3, 3, 5, 3 };``    ``int` `n = ``sizeof``(arr) / ``sizeof``(arr);``    ``cout << ``"Number of times 3 appears : "``         ``<< count(arr, arr + n, 3);`` ` `    ``return` `0;``}`
```Number of times 3 appears : 4
```

Counting occurrences in a vector.

 `// C++ program for count in C++ STL for``// a vector``#include ``using` `namespace` `std;`` ` `int` `main()``{``    ``vector<``int``> vect{ 3, 2, 1, 3, 3, 5, 3 };``    ``cout << ``"Number of times 3 appears : "``         ``<< count(vect.begin(), vect.end(), 3);`` ` `    ``return` `0;``}`
```Number of times 3 appears : 4
```

Counting occurrences in a string.

 `// C++ program for the count in C++ STL``// for a string``#include ``using` `namespace` `std;`` ` `int` `main()``{``    ``string str = ``"geeksforgeeks"``;`` ` `    ``cout << ``"Number of times 'e' appears : "` `         ``<< count(str.begin(), str.end(), ``'e'``);`` ` `    ``return` `0;``}`
```Number of times 'e' appears : 4
```

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