How do you swap two numbers without declaring temporary variable?

Question

Sigiloso · Accepted Answer

void swap( int &a, int &b )
{
a = a + b;
b = a - b;
a = a -b;
}

blakdogg · Answer

a = a ^ b
b = a ^ b
a = a ^ b

Sigiloso · Answer

Above will break on overflow...

Sigiloso · Answer

In Java...

int a;
int b;
{
  try {
    a += b;      \ a = a + b, might overflow
    b = a - b;   \ b = (a + b) - b
    a -= b;       \ a = (a + b) - (a)
  } catch (OverflowException e) {
    a -= b;       \ a = a - b, this might also overflow, but never if a + b overflows
    b += a;      \ b = b+ (a - b)
    a = b - a;   \ a = (a) - (a - b)
  }
}

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