What are the signs of crosses initialization?

Question

Consider the following code:

#include 
using namespace std;

int main()
{
    int x, y, i;
    cin >> x >> y >> i;
    swit         


        

Answer 1

I suggest you promote your r variable before the switch statement. If you want to use a variable across the case blocks, (or the same variable name but different usages), define it before the switch statement:

#include 
using namespace std;

int main()
{
    int x, y, i;
    cin >> x >> y >> i;
// Define the variable before the switch.
    int r;
    switch(i) {
        case 1:
            r = x + y
            cout << r;
            break;
        case 2:
            r = x - y;
            cout << r;
            break;
    };
}

One of the benefits is that the compiler does not have to perform local allocation (a.k.a. pushing onto the stack) in each case block.

A drawback to this approach is when cases "fall" into other cases (i.e. without using break), as the variable will have a previous value.