Variable initialization in for loop

Question

I had such a question:What is the difference between

int i;
for(i = 0; i < n; i++)

and

for(int i = 0; i < n; i++)

Does this influence memory and time?

Answer 1

Assuming you have written this code in the main function,

int i;
for(i = 0; i < n; i++)

In the case above, i is a local variable of the main function. If the value of i is updated in the loop it will remain updated even after the loop ends. i is not destroyed after the for loop. This is useful in some programs where you need the value of i after the loop for later use.

for(int i = 0; i < n; i++) 

In the case above, i is a local variable of the for loop. i will be destroyed once the loop is over.