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Memset array to 1 in C++

C++

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In this article, we have explored the problem of setting an array of int to 1 using memset in C++ and the solution for it.

Table of contents:

  1. Problem with memset
  2. Solution: Memset array to 1 in C++

Problem with memset

The problem is that memset sets the given value to each byte while an array of int or other datatype have multiple bytes. Consider the case of array of integers (int). Size of int is 4 bytes.

So, if we memset an array of int to 1 using the following code line:

memset(array, 1, size);

1 will be set to each byte. So, an int in the array will be like:

00000001 00000001 00000001 00000001

This binary representation results in the int value of (2^0 + 2^8 + 2^16 + 2^24) = 16843009. Hence, the memset is initializing the array of ints to 16843009. This is an issue which we have solved in this OpenGenus article.

Solution: Memset array to 1 in C++

The solution to initialize an array of int to 1 using memset is as follows:

  • Create an array of uint8_t datatype
  • Initialize the array of uint8_t to 1 using memset
  • Cast the uint8_t array to int array
uint8_t* array1 = (uint8_t *) malloc(size);
memset(array1, 1, size);
int* array2 = (int *) array1;

The array "array2" which is of datatype int will be initialize to 1 using memset.

Note: Performance-wise, this is not a recommended solution as it involves casting. Still, this will perform better than looping through an int array and setting each value to 1.

With this article at OpenGenus, you must have the complete idea of how to use memset to initialize an array of int to 1.

Geoffrey Ziskovin

Geoffrey Ziskovin

Geoffrey Ziskovin is an American Software Developer and Author with an experience of over 30 years. He started his career with Haskell and has interviewed over 700 candidates for Fortune 500 companies

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Memset array to 1 in C++
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