Allowed R6 · Within policy
{
"slug": "k-distinct-window",
"title": "K Distinct Window",
"difficulty": "medium",
"tags": [
"coding",
"oa",
"swe",
"intern"
],
"is_free": true,
"locked": false,
"frequency": 0.5,
"last_reported_at": "2026-07-23T11:54:29.490337Z",
"url": "https://www.mokabla.com/en/c/microsoft/k-distinct-window",
"agent": {
"page": "https://www.mokabla.com/agent/en/c/microsoft/k-distinct-window",
"question": "https://www.mokabla.com/agent/_call/get_question?company=microsoft&question=k-distinct-window"
},
"company": {
"slug": "microsoft",
"name_en": "Microsoft Egypt (ATLC)"
},
"body_md": "## Problem\nYou receive a string `s` and an integer `k`. Return the length of the longest contiguous substring of `s` that contains **at most `k` distinct characters**.\n\nI usually frame it as a log line: every character is an event type, and we want the longest stretch of the log that touches at most `k` different services.\n\n## Examples\n**Example 1**, `s = \"aabacbebebe\"`, `k = 3` → `7`\nThe window `\"cbebebe\"` holds `{c, b, e}` and has length 7. Extending it one step to the left pulls in `a` as a fourth type.\n\n**Example 2**, `s = \"aaaa\"`, `k = 1` → `4`\nThe whole string qualifies.\n\n**Edge**, `k = 0` → `0`, and an empty string → `0`.\n\n## Constraints\n- `1 <= len(s) <= 10^5`, lowercase ASCII.\n- `0 <= k <= 26`.\n- Target `O(n)` time and `O(k)` extra space.\n\n## What they look for\nTwo pointers plus a frequency map, shrinking from the left **only while** the distinct count exceeds `k`. The common slip is decrementing a count and forgetting to delete the key when it hits zero, which makes the distinct count wrong. Expect a follow-up asking for the substring itself rather than its length, and a question about why the loop is still linear even though there is a nested `while`.",
"follow_ups_md": "- Return the substring itself, not just its length.\n- Characters arrive as a stream: keep answering after every character.\n- Exactly `k` distinct instead of at most `k`.",
"access": "Question bodies are paid content: a person buys 30 days of access per company (200 EGP or 200 points) in the human app. Agents get titles, tags and difficulty; bodies only for free questions."
}