> ## 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.

# Boats to Save People Python Solution

> Tested Python solution for LeetCode 881 with 18 pytest cases. Generate a practice environment with lcpy.

LeetCode 881, Medium. Topics: Array, Two Pointers, Greedy, Sorting. [View on LeetCode](https://leetcode.com/problems/boats-to-save-people/description/).

Generate this problem as a practice environment: tested reference solution, 18 [parametrized pytest cases](/practice/testing), and a playground notebook:

```bash theme={"theme":{"light":"github-light","dark":"github-dark"}}
lcpy gen -n 881   # by problem number
lcpy gen -s boats_to_save_people   # by problem name
```

## Problem

You are given an array `people` where `people[i]` is the weight of the `i^th` person, and an **infinite number of boats** where each boat can carry a maximum weight of `limit`. Each boat carries at most two people at the same time, provided the sum of the weight of those people is at most `limit`.

Return *the minimum number of boats to carry every given person*.

### Examples

```
Input: people = [1,2], limit = 3
Output: 1
Explanation: 1 boat (1, 2)
```

```
Input: people = [3,2,2,1], limit = 3
Output: 3
Explanation: 3 boats (1, 2), (2) and (3)
```

```
Input: people = [3,5,3,4], limit = 5
Output: 4
Explanation: 4 boats (3), (3), (4), (5)
```

### Constraints

* 1 \<= people.length \<= 5 \* 10^4
* 1 \<= people\[i] \<= limit \<= 3 \* 10^4

## Solution

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

```python theme={"theme":{"light":"github-light","dark":"github-dark"}}
class Solution:
    # Time: O(n log n)
    # Space: O(n) for sorting
    def num_rescue_boats(self, people: list[int], limit: int) -> int:
        people.sort()
        boats = 0
        left, right = 0, len(people) - 1
        while left <= right:
            if people[left] + people[right] <= limit:
                left += 1
            right -= 1
            boats += 1
        return boats
```

## Complexity

| Time       | Space            |
| ---------- | ---------------- |
| O(n log n) | O(n) for sorting |

## Tags

[NeetCode 250](/catalog/neetcode-250), [NeetCode All](/catalog/neetcode).