How to Efficiently Initialize All Array Elements to a Default Value in C ?

Initialization of All Array Elements to a Default Value

In C , you can initialize all elements of an array to a default value using the following syntax:

int array[100] = {0};

This will set all elements of the array to 0. However, you may encounter unexpected behavior when attempting to initialize all elements to a non-zero value, such as -1.

Setting All Elements to a Non-Zero Value

The syntax:

int array[100] = {-1};

instructs the compiler to set only the first element to -1, while the remaining elements will default to 0. To initialize all elements to -1, you can use methods like:

• std::fill_n (C Standard Library):

std::fill_n(array, 100, -1);

• Loop-Based Initialization (Portable C):

for (int i = 0; i < 100; i++) {
  array[i] = -1;
}

Performance Consideration

Whether default initialization is faster than a loop-based approach depends on factors such as the compiler and the target platform. In general, modern compilers can optimize away loop-based initialization by using platform-specific intrinsics. Therefore, the performance difference is often negligible.

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