## Overview
Relevant problems for myself
- 🎨 Guides
- âš¡ Solutions
- ♿ Patterns
## The Golden Rule (Memorize This)
**Only sort if the problem asks for ORDER or RANKING.**
If the problem asks for:
- "first"
- "index"
- "position"
- "does it exist"
- "true/false"
- "count how many"
→ **DO NOT SORT**. Just use the frequency map and loop.
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## Decision Cheat Sheet
| What the problem wants | Do you need to sort? | What to do instead | Example Problem |
|-----------------------------------------|----------------------|-------------------------------------|---------------------|
| Sort characters by how often they appear | YES | Freq + Sort | LC 451 |
| Top K most frequent | YES | Freq + Sort + slice | LC 347 |
| Sort array by frequency | YES | Freq + Sort | LC 1636 |
| First unique character (index) | NO | Freq + loop original string | LC 387 |
| Is it an anagram? | NO | Freq + check counts | LC 242 |
| How many numbers smaller than current | Kind of | Freq + prefix count | LC 1365 |
| Most frequent element | NO | Freq + find max | LC 169 |
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## Mental Checklist (Say this out loud every time)
1. "Did I count the frequencies?" → Yes
2. "Does the problem care about the **original order**?"
- Yes → Loop the original string/array and check freq
- No → You can sort
3. "Does it want an **index** or a **boolean**?"
- Yes → Almost never sort
4. "Does it want the elements **re-ordered**?"
- Yes → Sort by frequency
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## Super Short Version to Tattoo in Your Brain
**"If it wants the first / index / true-false → loop original.
If it wants sorted / top k / reordered → sort."**
---
## Practice Trigger Words
- "first non-repeating" → Loop original
- "return its index" → Loop original
- "sort by frequency" → Sort
- "top k frequent" → Sort + slice
- "valid anagram" → Just check counts