You can swap two integers in C++ without using a third variable in several ways, but each method has caveats. Here are the common approaches:

1. Using arithmetic operations

a = a + b;
b = a - b;
a = a - b;

Pros:

• No extra variable needed.

Cons:

• Can cause integer overflow if a + b exceeds the integer limit.

2. Using XOR (bitwise swap)

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

Pros:

• No overflow issues.

• Does not require extra space.

Cons:

• Does not work if a and b refer to the same memory location (e.g., swapping the same variable).

• Less readable than normal swap.

3. Using std::swap (recommended)

std::swap(a, b);

Pros:

• Most readable and safest method.

• Modern compilers optimize it very well.

Cons:

• Uses a temporary variable internally (but that’s usually fine).