Most elegant way to change 0 to 1 and vice versa
i ^= 1;
XOR the value with 1. This gives you both ways (in case you need to flip 0 <--> 1 either way):
0 ^ 1 = 1
1 ^ 1 = 0
subtraction?
i = 1 - i;
i = (i == 0)?1:0 is one way, though I like @Jimmy's and @Yuval's versions better.
i = ( i + 1 ) % 2, though I think we all agree the subtraction or xor method is better! (Though it has the added benefit of "flipping the switch" for more than binary.)
Use Bitwise XOR operator:
i ^= 1;