> ## Documentation Index
> Fetch the complete documentation index at: https://leetcode-py.wisl.dev/llms.txt
> Use this file to discover all available pages before exploring further.

> ## Agent Instructions
> leetcode-py is a Python LeetCode practice environment generator with one CLI: lcpy. It is not a service or platform.
> Each problem is a directory under leetcode/ with README.md, solution.py, test_solution.py, helpers.py, and playground.ipynb. lcpy gen creates them from JSON templates bundled with the package.
> Examples are backed by tests; copy them verbatim.

# Binary Search Python Solution with Tests

> Tested Python solution for LeetCode 704 with 13 pytest cases. Generate a practice environment with lcpy.

LeetCode 704, Easy. Topics: Array, Binary Search. [View on LeetCode](https://leetcode.com/problems/binary-search/description/).

Generate this problem as a practice environment: tested reference solution, 13 [parametrized pytest cases](/practice/testing), and a playground notebook:

```bash theme={"theme":{"light":"github-light","dark":"github-dark"}}
lcpy gen -n 704   # by problem number
lcpy gen -s binary_search   # by problem name
```

## Problem

Given an array of integers `nums` which is sorted in ascending order, and an integer `target`, write a function to search `target` in `nums`. If `target` exists, then return its index. Otherwise, return `-1`.

You must write an algorithm with `O(log n)` runtime complexity.

### Examples

```
Input: nums = [-1,0,3,5,9,12], target = 9
Output: 4
```

**Explanation:** 9 exists in nums and its index is 4

```
Input: nums = [-1,0,3,5,9,12], target = 2
Output: -1
```

**Explanation:** 2 does not exist in nums so return -1

### Constraints

* `1 <= nums.length <= 10^4`
* `-10^4 < nums[i], target < 10^4`
* All the integers in `nums` are **unique**.
* `nums` is sorted in ascending order.

## Solution

Reference implementation from [solution.py on GitHub](https://github.com/wislertt/leetcode-py/blob/main/leetcode/binary_search/solution.py), full suite in [test\_solution.py](https://github.com/wislertt/leetcode-py/blob/main/leetcode/binary_search/test_solution.py):

```python theme={"theme":{"light":"github-light","dark":"github-dark"}}
class Solution:
    # Time: O(log n)
    # Space: O(1)
    def search(self, nums: list[int], target: int) -> int:
        left, right = 0, len(nums) - 1

        while left <= right:
            mid = (left + right) // 2

            if nums[mid] == target:
                return mid
            elif nums[mid] < target:
                left = mid + 1
            else:
                right = mid - 1

        return -1
```

## Complexity

| Time     | Space |
| -------- | ----- |
| O(log n) | O(1)  |

## Tags

[Grind 75](/catalog/grind-75), [Grind](/catalog/grind), [NeetCode 150](/catalog/neetcode-150), [NeetCode 250](/catalog/neetcode-250), [NeetCode All](/catalog/neetcode).