Find a Digit in the Concatenated Positive Integers
Company: Google
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: medium
Interview Round: Other
# Find a Digit in the Concatenated Positive Integers
Write the positive integers consecutively in decimal:
```text
123456789101112131415...
```
Given `n`, return the digit at the one-based position `n` in this infinite digit sequence.
### Function
`int findNthDigit(int n)`
### Example 1
```text
Input: n = 15
Output: 2
```
Positions `14` and `15` are the digits of `12`, so position `15` contains `2`.
### Example 2
```text
Input: n = 190
Output: 1
```
The one-digit integers contribute `9` digits, and the two-digit integers contribute `180`. Position `190` is the first digit of `100`.
### Example 3
```text
Input: n = 1
Output: 1
```
### Constraints
- `1 <= n <= 2147483647`.
### Clarifications
Positions count individual digits, not integers. Return a digit as an integer from `0` through `9`, not a string or the whole number containing it.
### What a Strong Answer Covers
- One-based positioning and boundaries between decimal lengths.
- Selecting the exact digit within its containing number.
- Correctness and safe arithmetic near the maximum position.
- Time and storage bounds.
Overview: Practice locating a one-based digit in the concatenation of positive decimal integers. Handle number-length boundaries and large positions without constructing the sequence.