# Count the number of 1’s and 0’s in a binary array using STL in C++ ?

Given a binary array, the task is to count the number of 1’s and 0’s in this array using STL in C++.

**Examples:**

Input:arr[] = {1, 0, 0, 1, 0, 0, 1}Output:1's = 3, 0's = 4Input:arr[] = {1, 1, 1, 1, 0, 0, 1}Output:1's = 5, 0's = 2

**Approach:** We can count the same using count_if() function present in the STL of C++.

**Syntax:**

count_if(lower_bound, upper_bound, filter_function) where filter_function is a condition which filters out elements.

Below is the implementation of the above approach:

`// C++ program to Count ` `// the number of 1's and 0's ` `// in a binary array ` ` ` `#include <bits/stdc++.h> ` `using` `namespace` `std; ` ` ` `// Function to check ` `// if bit is 1 or not ` `bool` `isOne(` `int` `i) ` `{ ` ` ` `if` `(i == 1) ` ` ` `return` `true` `; ` ` ` `else` ` ` `return` `false` `; ` `} ` ` ` `// Driver Code ` `int` `main() ` `{ ` ` ` ` ` `int` `a[] = { 1, 0, 0, 1, 0, 0, 1 }; ` ` ` ` ` `int` `n = ` `sizeof` `(a) / ` `sizeof` `(a[0]); ` ` ` ` ` `int` `count_of_one = count_if(a, a + n, isOne); ` ` ` ` ` `cout << ` `"1's: "` `<< count_of_one << endl; ` ` ` `cout << ` `"0's: "` `<< (n - count_of_one) << endl; ` ` ` ` ` `return` `0; ` `} ` |

*chevron_right*

*filter_none*

**Output:**

1's: 3 0's: 4

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