Sum of Digits in the Minimum Number

Sum of Digits in the Minimum Number

What is this problem about?

The "Sum of Digits in the Minimum Number" problem involves two steps. First, you are given an array of integers and you must find the minimum value in that array. Second, you calculate the sum of the digits of that minimum value. Finally, you return 1 if the sum is even, and 0 if the sum is odd. For example, if the array is [34, 23, 12], the minimum is 12. The sum of digits of 12 is 1 + 2 = 3. Since 3 is odd, you return 0.

Why is this asked in interviews?

This is a common "warm-up" question used by Amazon. It tests two very basic but essential skills: finding an extremum (minimum) in an array and extracting digits from an integer. It evaluates if a candidate can follow a multi-step instruction set clearly and write concise, bug-free code for simple operations.

Algorithmic pattern used

The pattern involves:

1. Linear Search: Iterate through the array once to find the minimum element.
2. Digit Extraction: Use the % 10 and / 10 loop to calculate the sum of digits of that minimum element.
3. Parity Check: Use the % 2 operator on the final sum to determine if it is even or odd.

Example explanation

Given array: [99, 77, 33].

1. Find minimum: Iterate through the array. 33 is the smallest.
2. Sum digits of 33:
   • 33 % 10 = 3.
   • 3 % 10 = 3.
   • Sum = 3 + 3 = 6.
3. Check parity: 6 % 2 is 0, which means it is even. Return 1.

Common mistakes candidates make

1. Inefficient Sorting: Sorting the entire array just to find the minimum. Finding the minimum should take O(N) time, whereas sorting takes O(N log N).
2. Incorrect Summation: Forgetting to reset the sum variable or incorrectly handling the loop that extracts digits.
3. Misinterpreting the return value: Returning the sum itself instead of 1 or 0 based on whether the sum is even or odd.

Interview preparation tip

For "Easy" problems, focus on speed and clarity. Don't use complex library functions when a simple loop will do. Interviewers look for "clean" solutions that handle all parts of the question precisely without over-engineering.