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Grokking the Coding Interview Patterns

Solution: String Compression

Understand how to apply the two pointers technique to compress a string in place by encoding consecutive characters. Learn to modify the input array efficiently, using constant space while achieving linear time performance.

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Statement

Given an array of characters, chars, compress it in place according to the following rules:

  1. Start with an empty string s.

  2. For each group of consecutive repeating characters in chars:

    1. If the group length is 11, append just the character to s.

    2. Otherwise, append the character followed by the group length.

The compressed string s should not be returned separately; instead, it must be written directly into the input character array chars. Note that if a group’s length is 1010 ...