> ## 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.

# Word Break Python Solution with Tests

> Tested Python solution for LeetCode 139 with 15 pytest cases. Generate a practice environment with lcpy.

LeetCode 139, Medium. Topics: Array, Hash Table, String, Dynamic Programming, Trie, Memoization. [View on LeetCode](https://leetcode.com/problems/word-break/description/).

Generate this problem as a practice environment: tested reference solution, 15 [parametrized pytest cases](/practice/testing), and a playground notebook:

```bash theme={"theme":{"light":"github-light","dark":"github-dark"}}
lcpy gen -n 139   # by problem number
lcpy gen -s word_break   # by problem name
```

## Problem

Given a string `s` and a dictionary of strings `wordDict`, return `true` if `s` can be segmented into a space-separated sequence of one or more dictionary words.

**Note** that the same word in the dictionary may be reused multiple times in the segmentation.

### Examples

```
Input: s = "leetcode", wordDict = ["leet","code"]
Output: true
```

**Explanation:** Return true because "leetcode" can be segmented as "leet code".

```
Input: s = "applepenapple", wordDict = ["apple","pen"]
Output: true
```

**Explanation:** Return true because "applepenapple" can be segmented as "apple pen apple".
Note that you are allowed to reuse a dictionary word.

```
Input: s = "catsandog", wordDict = ["cats","dog","sand","and","cat"]
Output: false
```

### Constraints

* `1 <= s.length <= 300`
* `1 <= wordDict.length <= 1000`
* `1 <= wordDict[i].length <= 20`
* `s` and `wordDict[i]` consist of only lowercase English letters.
* All the strings of `wordDict` are **unique**.

## Solution

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

```python theme={"theme":{"light":"github-light","dark":"github-dark"}}
class Solution:
    # Time: O(n^2)
    # Space: O(n)
    def word_break(self, s: str, word_dict: list[str]) -> bool:
        word_set = set(word_dict)
        dp = [False] * (len(s) + 1)
        dp[0] = True

        for i in range(1, len(s) + 1):
            for j in range(i):
                if dp[j] and s[j:i] in word_set:
                    dp[i] = True
                    break

        return dp[-1]
```

## Complexity

| Time   | Space |
| ------ | ----- |
| O(n^2) | O(n)  |

## Tags

[Grind 75](/catalog/grind-75), [Grind](/catalog/grind), [Blind 75](/catalog/blind-75), [NeetCode 150](/catalog/neetcode-150), [NeetCode 250](/catalog/neetcode-250), [NeetCode All](/catalog/neetcode), [AlgoMaster 75](/catalog/algo-master-75).