Swapping 2 variables(numbers, characters, strings, booleans) without using extra variable

Rahul Parshi — Sun, 14 Feb 2021 10:58:11 +0000

Numbers

        a = a + b;
        b = a - b;      // (a+b) - (b) = a
        a = a - b;      // (a+b) - (a) = b

        a = a ^ b;
        b = a ^ b;      // (a ^ b) ^ (b) = a ^ 0 = a 
        a = a ^ b;      // (a ^ b) ^ (a) = 0 ^ b = b

If characters are stored with it's ASCII value like C++, same method as numbers can be used. Else characters can be type caste to numbers.

        a = (char) ((int)a ^ (int)b);
        b = (char) ((int)a ^ (int)b);    
        a = (char) ((int)a ^ (int)b);

        a = a + b;      
        b = a.substr(0, (a.length() - b.length()));   
        a = a.substr(b.length(), a.length());

Space complexity = S(M + N) where M is length of a and N is length of b;

If both the variables are same, swapping is not required else need to toggle the values.

        if (a != b){
            a = true ^ a;   //toggles the value
            b = true ^ b;
        }