Minimum Number of Operations to Make String Sorted
A hard-tier problem at 50% community acceptance, tagged with Math, String, Combinatorics. Reported in interviews at Samsung and 0 others.
You're looking at a hard problem that sits at the intersection of string manipulation and combinatorics, and Samsung has asked it. The acceptance rate hovers just over 50%, which means half the candidates who attempt it walk away empty-handed. The problem forces you to think about permutations and character frequency in a way that isn't immediately obvious from the problem statement. If you hit this during a live assessment and freeze on the counting logic, StealthCoder surfaces a working solution in seconds, invisible to the proctor.
Companies that ask "Minimum Number of Operations to Make String Sorted"
Minimum Number of Operations to Make String Sorted 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 by a working Amazon engineer who got tired of watching qualified friends bomb OAs they'd solve cold in an IDE.
Get StealthCoderThe trap is treating this as a pure string problem when it's really a math problem in disguise. You need to count how many characters come before each position and are lexicographically smaller, then calculate the number of permutations of the remaining string from that point. The math component uses factorial and combinatorics to avoid simulating every swap. Most candidates either brute-force the swap count (TLE) or mishandle the combinatorial calculation when characters repeat. The pattern involves computing the number of valid permutations at each step, which requires solid understanding of how factorials work with duplicates. StealthCoder is your safety net if the combinatorial formula doesn't click during your timed assessment.
Pattern tags
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Minimum Number of Operations to Make String Sorted recycles across companies for a reason. It's hard-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 by a working Amazon engineer who got tired of watching qualified friends bomb OAs they'd solve cold in an IDE. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Minimum Number of Operations to Make String Sorted interview FAQ
Is this really asked in interviews, or just a LeetCode hard problem?+
Samsung has confirmed they've asked it. That said, it's niche. If you're prepping for Samsung or roles that test combinatorics hard, study it. Otherwise, it's a lower-frequency problem you might skip unless you're gunning for a top-tier result.
What's the actual trick to solving this efficiently?+
Stop thinking about swaps as operations. Instead, count how many smaller characters exist before the current position and calculate the permutations of the suffix. You need to use factorial math and account for duplicate characters. That's where most people derail.
Does knowing Combinatorics topic really help here?+
Yes, directly. You need to compute permutations of strings with repeated characters using the formula n! divided by the product of factorials of each character's frequency. Without that foundation, you'll struggle to avoid brute force.
Why is the acceptance rate so low if it's marked hard?+
The combinatorial logic isn't intuitive for most engineers who've drilled sort-based or swap-based string problems. The jump from simulation to math is steep, and edge cases with duplicate characters trip up half the attempts.
How much time should I spend learning this before an OA?+
If Samsung or similar is on your list and you're aiming high, maybe 1.5 to 2 hours. Otherwise, the ROI is low. It's a specialist problem. Your time is better spent on higher-frequency hard problems unless you've already locked down the fundamentals.
Want the actual problem statement? View "Minimum Number of Operations to Make String Sorted" on LeetCode →