Longest run of one character

Question

Given a string, return the length of the longest run of a single repeated character (consecutive identical characters). An empty string has a longest run of 0.

"aabbbbcc"     ->  4     # the run of b's
"abcabc"       ->  1     # no character repeats consecutively
""             ->  0

Return the longest run length in $O(n)$ time and $O(1)$ space.

Accepted Answer

Same run-detection walk as run-length compression, but instead of emitting each run you just track the longest one. Compare each character to the one before it: if equal, extend the current run; otherwise reset the current run to length 1. Keep a running best. Tracing "aabbbbcc": run lengths climb 1, 2 (a's), reset then 1, 2, 3, 4 (b's), reset then 1, 2 (c's). The best seen is 4. Time O(n), space O(1). Because we only need the maximum, there is no output buffer, so this is constant space unlike the compression itself. Takeaway. Detecting runs by comparing each element to its predecessor is th…

Longest run of one character

Your answer

More Coding questions