class Solution:
    def encode(self, strs: list[str]) -> str:
        # Efficiently join all "length:string" segments
        return "".join(f"{len(s)}:{s}" for s in strs)
 
    def decode(self, s: str) -> list[str]:
        decoded = []
        i = 0
        while i < len(s):
            # find the colon
            j = s.find(":", i)
            length = int(s[i:j])              # parse length
            word = s[j+1:j+1+length]          # extract word
            decoded.append(word)
            i = j + 1 + length                # move to next segment
        return decoded
 

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