Count of Integers
A hard-tier problem at 37% community acceptance, tagged with Math, String, Dynamic Programming. Reported in interviews at Morgan Stanley and 1 others.
Count of Integers is a hard problem that appears in Morgan Stanley and Cisco interviews. With a 37% acceptance rate, it's a serious filter. The catch: most people default to brute force on the first read, and it'll time out immediately. The trick lives in the intersection of string manipulation and dynamic programming. You need to recognize that iterating through every integer in a range is a non-starter. This is exactly the kind of problem where a clean DP insight separates the pass from the timeout. If you hit this live and blank on the state transition, StealthCoder solves it invisibly during your screen share.
Companies that ask "Count of Integers"
Count of Integers 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. Built by an Amazon engineer who realized the OA tests how well you memorized 200 problems, not how well you code.
Get StealthCoderThis problem demands digit DP, a pattern that's easy to miss if you haven't seen it before. The core insight: represent the problem as counting valid numbers by their string form, building answers digit by digit from left to right. You'll track whether you're still bounded by the upper limit and whether you've started placing non-zero digits. The gotcha is the state space, not the string logic. Many candidates implement a recursive solution correctly but fail to memoize properly or miss that leading zeros matter. Another common pitfall is mixing up inclusive and exclusive bounds. The problem pulls from Math, String, and Dynamic Programming because you need all three: math intuition for the boundary cases, string operations for digit iteration, and DP for the exponential state explosion. When this hits your assessment and you're stuck between three wrong approaches, StealthCoder surfaces the clean digit DP template in seconds.
Pattern tags
You know the problem.
Make sure you actually pass it.
Count of Integers 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. Built by an Amazon engineer who realized the OA tests how well you memorized 200 problems, not how well you code. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Count of Integers interview FAQ
Is digit DP the only way to solve this?+
Yes, for the hard difficulty and acceptance rate here. Brute force enumeration fails because the range is too large. Digit DP is the standard pattern. If you don't know it going in, the live OA is the worst place to invent it.
Do Morgan Stanley and Cisco ask this problem the same way?+
Both companies' reports list it, but variants exist. The core skill tested remains the same: recognizing range-counting problems that require digit DP, not iteration. Master the pattern and you're covered.
What's the most common mistake on the DP state?+
Forgetting to track whether you're still bounded by the limit, or not handling leading zeros correctly. These two decisions define your state transitions. Get them wrong and your answer is off by orders of magnitude.
How does this differ from other hard DP problems?+
Most hard DP problems work on trees or 2D grids. Digit DP is special because the state space is the string representation of numbers. It's more abstract and less intuitive until you've seen it once.
Can I practice this in isolation or do I need the full range context?+
You need the full context. The range bounds are what make digit DP necessary. A simpler counting problem without bounds teaches nothing here. Practice digit DP templates on a few variants to build muscle memory.
Want the actual problem statement? View "Count of Integers" on LeetCode →