Check if All elements in Array are equal to value in C++

This tutorial will discuss about a unique way to check if all elements in array are equal to value in C++.

To check if all elements of array matches with a given value, we are going to use the STL algorithm std::all_of().

Inside STL algorithm std::all_of() we will pass 3 arguments,

• Pointer pointing to the start of array.
• Pointer pointing to the end of array
• A Lambda function, which accepts an element as an argument and returns true if the given element is equal to a given value.

The std::all_of() function will apply the given Lambda function on all the elements of the array. If for all the elements the lambda function returns true, then the std::all_of() function will return true.

If there is a single element in array that is not equal to the given value, then the std::all_of() function returns false.

Like, in the below example we will check if all the elements of array are equal to value 15.

Let’s see the complete example,

#include <iostream>
#include <algorithm>

int main()
{
    int arr[] = { 15, 15, 15, 15, 15 };

    int value = 15;

    // Get the size of array
    size_t len = sizeof(arr)/sizeof(arr[0]);

    // Check if all elements of array arr are equal to a value
    bool result = std::all_of(arr,
                              arr + len,
                              [&value](bool elem){
                                    return elem == value;
                              });

    if (result)
    {
        std::cout << "Yes, all elements of array are equal to 15." << std::endl;
    }
    else
    {
        std::cout << "No, all elements of array are not equal to 15." << std::endl;
    }

    return 0;
}

Output :

No, all elements of array are not equal to 15.

Summary

Today we learned about several ways to check if all elements in array are equal to value in C++. Thanks.