Encode and Decode Strings — Step-by-Step Visualization

Algorithm Pattern

Length Prefixed Encoding

Key Idea

To distinguish between the separator and the content of the strings, we prepend each string with its length follow by a special character (e.g., `#`). For example, `hello` becomes `5#hello`. During decoding, we read the length until we hit `#`, then read the guaranteed number of characters specified by that length.

Step-by-Step Approach

1. Encode:
2. For each string `s`, append `len(s) + '#' + s` to a result string.
3. Decode:
4. Use a pointer `i` to traverse the encoded string.
5. Find the next `#` starting from `i` to get the length `n`.
6. Extract the substring from `index of # + 1` with length `n`.
7. Move `i` past the extracted substring and repeat.

Common Gotchas

• The '#' character itself can be inside the string; the length prefix prevents ambiguity.
• Empty strings should be handled (e.g., `0#`).