Encode and Decode Strings
The problem
Design encode(words) and decode(data) so any list of strings can be converted to one string and recovered exactly. Strings may be empty or contain your delimiter.
Example
["a#b", "", "cat"] → "3#a#b0#3#cat" → original list
Need a hint?
A delimiter alone fails when the payload contains that delimiter.
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Read the solution approach
Write each string’s length, a separator, then the string. To decode, read digits up to the separator, then consume exactly that many characters. Repeat until the encoded input ends. Use the same length unit in encoder and decoder, and collect pieces before joining to avoid quadratic concatenation.
Complexity
O(total payload length + length-prefix characters) time and space.
Before moving on, explain why the algorithm is correct and trace a boundary case without looking at the approach.