leetcode/apps/docs/content/array/271-encode-and-decode-strings.mdx

---
title: '271. Encode and Decode Strings'
description: Design an algorithm to encode a list of strings to a string. The encoded string is then sent over the network and is decoded back to the original list of strings
sidebar:
  label: 'Encode and Decode Strings'
  badge: 'Medium'
---

<Badge variant="accent">Array</Badge>

::::warning
Could you write a generalized algorithm to work on any possible set of characters?
::::

### Example 1:
- Input: `dummy_input = ["Hello","World"]`
- Output: `["Hello","World"]`
- Explanation: Machine `1`: Codec encoder = new Codec(); String msg = encoder.encode(strs); Machine `1` ---msg---> Machine `2` Machine `2`: Codec decoder = new Codec(); `String[] strs` = decoder.decode(msg);

### Example 2:
- Input: `dummy_input = [""]`
- Output: `[""]`

### Constraints:

- `1 <= strs.length <= 200`
- `0 <= strs[i].length <= 200`
- `strs[i]` contains any possible characters out of 256 valid ASCII characters.

## Approach

::::warning
The diagram traces the code below literally. That code does not solve the problem: both `encode` and `decode` have only a docstring for a body, so each returns `None` and `codec.decode(codec.encode(strs))` yields `None` instead of `strs`.
::::

```mermaid
flowchart TD
  subgraph state["state — Codec holds no fields"]
    X["Codec() — nothing is stored between encode and decode"]
  end
  subgraph encode["encode(strs)"]
    E1["docstring only — no statement runs"] --> E2(["return None"])
  end
  subgraph decode["decode(s)"]
    D1["docstring only — no statement runs"] --> D2(["return None"])
  end
  state --> encode
  state --> decode
```

## Solution

```py
class Codec:
    def encode(self, strs: List[str]) -> str:
        """Encodes a list of strings to a single string.
        """
        

    def decode(self, s: str) -> List[str]:
        """Decodes a single string to a list of strings.
        """
        


# Your Codec object will be instantiated and called as such:
# codec = Codec()
# codec.decode(codec.encode(strs))
```

## Explanation

<YouTube id="B1k_sxOSgv8" title="Encode and Decode Strings - Leetcode 271 - Python" />