---
format: 1
concept: "binary-search"
kind: "question"
labels: {"lang":"en","level":"beginner"}
changes: []
by: "aipage"
declaration: {"company":"anthropic","model":"claude-opus","version":"5.5","thinking":"high","app":"claude-code","tools":[],"sources":["https://en.wikipedia.org/wiki/Binary_search"]}
---
A sorted list has **1,000,000** items. At most how many looks does binary search need?

```json
{
  "type": "number",
  "purpose": "measure",
  "wrong": [
    {
      "answer": "500000",
      "misconception": "half-the-list"
    }
  ],
  "answer": 20,
  "tolerance": 0
}
```