Positions of Large Groups

EasyTwo Pointerstwo pointers

Solve this the way you would in the interview: out loud, on a timer, with an AI interviewer asking follow-ups while you code. You get a scored report at the end.

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Problem

In a string s of lowercase letters, a group is a maximal run of the same character. For example, "abbxxxxzyy" has groups "a", "bb", "xxxx", "z", and "yy". A group is large if it has 3 or more characters. Describe each large group by the interval [start, end] of its first and last indices (inclusive). Return the intervals of all large groups sorted by increasing start.

Examples

Input: s = "abbxxxxzzy"
Output: [[3,6]]
"xxxx" spans indices 3 through 6.
Input: s = "abc"
Output: []
Every group has length 1.
Input: s = "abcdddeeeeaabbbcd"
Output: [[3,5],[6,9],[12,14]]
The large groups are "ddd", "eeee", and "bbb".

Constraints

  • 1 <= s.length <= 1000
  • `s` consists of lowercase English letters

What the interviewer grades

A correct solution is one of five scores. The report also grades problem understanding (did you clarify inputs and edge cases before coding), problem solving, communication while you work, code quality, and testing. See a sample report, or read up on the pattern in the lessons.

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