Question

How to swap 2 numbers without a 3rd variable?

I'm trying to understand how to swap two numbers without using a third variable. I’ve heard it’s possible through arithmetic or bitwise operations, but I’m unsure of the exact steps. What’s the best approach to swap values efficiently without needing extra storage?

Answer 1

Suppose we have two numbers, 5 and 3.

Let:

a = 5 (First number)
b = 3 (Second number)

Swapping Logic:
a = a + b = 5 + 3 = 8
b = a - b = 8 - 3 = 5
a = a - b = 8 - 5 = 3
After swapping, the values are:

a = 3
b = 5

Algorithm:
STEP 1: START
STEP 2: ENTER a, b
STEP 3: PRINT initial values of a, b
STEP 4: a = a + b
STEP 5: b = a - b
STEP 6: a = a - b
STEP 7: PRINT swapped values of a, b
STEP 8: END

javascript code:

let a = 5; // First number
let b = 3; // Second number

console.log("Before swapping:");
console.log("a =", a);
console.log("b =", b);

// Swapping Logic
a = a + b;  // Step 4: a becomes 8 (5 + 3)
b = a - b;  // Step 5: b becomes 5 (8 - 3)
a = a - b;  // Step 6: a becomes 3 (8 - 5)

console.log("After swapping:");
console.log("a =", a);
console.log("b =", b);