How should I practice Decode String?

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Problem · String

Decode String

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Problem statement

Given a valid encoded string s, return its fully decoded form.

The encoding rule is k[encoded_string], meaning that the content inside the brackets is repeated exactly k times. Encoded groups may be nested, and adjacent literal or encoded groups are concatenated.

The problem statement continues

Pro

Examples

Example 1

s = "3[a2[c]]"return = "accaccacc"

The inner group 2[c] becomes cc, so the outer group is 3[acc].

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