Python Coding challenge - Day 534| What is the output of the following Python Code?

 

Code Explanation:

Function Definition

def single_number(nums):

This line defines a function called single_number.

It takes one parameter: nums, which is a list of integers.

Initialize Result Variable

    result = 0

Initializes a variable result to 0.

This will store the final answer using the XOR operation.

Iterate Over All Numbers

    for n in nums:

This starts a loop to go through each number n in the input list nums.

Bitwise XOR Operation

        result ^= n

^= is a bitwise XOR assignment operator.

It means: result = result ^ n

XOR has some important properties:

a ^ a = 0 (a number XOR itself is zero)

a ^ 0 = a (a number XOR zero is the number itself)

XOR is commutative and associative, so order doesn't matter.

So, pairs cancel each other out, and the number that appears only once remains.

Return the Result

    return result

After looping through all numbers, result holds the number that appears only once.

This line returns that number.

Function Call and Output

print(single_number([4, 1, 2, 1, 2]))

Calls the function with the list [4, 1, 2, 1, 2]

The numbers 1 and 2 appear twice, so they cancel out.

Only 4 appears once, so the output will be:

4

Final Output

4

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