Count Integers With Even Digit Sum
A easy-tier problem at 69% community acceptance, tagged with Math, Simulation. Reported in interviews at MindTree and 0 others.
Count Integers With Even Digit Sum is an easy problem that's been asked at MindTree and appears in most screening assessments. It's not hard, but the acceptance rate sits at 69%, which means plenty of candidates either overthink it or miss the pattern. The problem asks you to count how many integers in a range have digits that sum to an even number. Sounds straightforward until you realize brute force might timeout on large ranges. If this hits your live OA and you blank on the optimization, StealthCoder surfaces a working solution in seconds, invisible to the proctor.
Companies that ask "Count Integers With Even Digit Sum"
Count Integers With Even Digit Sum is the kind of problem that decides whether you pass. StealthCoder reads the problem on screen and surfaces a working solution in under 2 seconds. Invisible to screen share. The proctor sees nothing. Made for the engineer who has done the work but might still blank with a webcam pointed at him.
Get StealthCoderThe obvious trap is iterating through every number in the range, summing digits, and checking parity. That works for small ranges but fails fast at scale. The real trick is recognizing the pattern: in any consecutive 10 integers, exactly 5 have even digit sums and 5 have odd ones. This Math observation collapses the problem from simulation to arithmetic. Once you see it, you can compute the answer in O(1) or O(log n) time instead of O(n). The pitfall is getting stuck in simulation mode and not stepping back to find the mathematical structure. StealthCoder is your hedge for the moment you realize brute force won't pass the test cases.
Pattern tags
You know the problem.
Make sure you actually pass it.
Count Integers With Even Digit Sum recycles across companies for a reason. It's easy-tier, and most candidates blank under the timer. StealthCoder is the hedge: an AI overlay invisible during screen share. It reads the problem and surfaces a working solution in under 2 seconds. Made for the engineer who has done the work but might still blank with a webcam pointed at him. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Count Integers With Even Digit Sum interview FAQ
Is this problem really easy or will it catch me off guard?+
It's labeled easy but the 69% acceptance rate suggests it catches people. Most miss the pattern and timeout on brute force. The problem is simple once you spot the Math trick, which isn't obvious under pressure.
What's the actual trick to solving this efficiently?+
Recognize that digit sum parity repeats every 10 consecutive integers: 5 are even, 5 are odd. Use this pattern to compute ranges in constant time instead of iterating through every number.
Will MindTree ask follow-ups on this problem?+
MindTree is the only company in the input data that's asked this. At easy level with this acceptance rate, they're testing whether you can spot the pattern under time pressure, not necessarily chaining complex follow-ups.
How does simulation fit into the optimal solution?+
Simulation is the brute-force fallback: check each integer, sum its digits, count even sums. It's correct but slow on large ranges. The optimal approach replaces simulation with Math by exploiting the parity pattern.
Should I just code the brute force and hope it passes?+
Only if the range is tiny. Most assessments will have test cases large enough to timeout brute force. The Math pattern is what separates accepted solutions from TLE verdicts at this problem level.
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