Tech Support / L1-L3

Why are indexes not created on all columns and all combinations in a row?

In what cases are indexes appropriate?

Difference between a process and a thread.

What types of non-relational databases exist and for what tasks are they used? How do they differ from relational databases?

How to fight race conditions?

What is a hash table?

/** * Repeating characters * * Write a function that takes a string as input and returns * for each unique character the maximum number of its consecutive repetitions. * * Input: aaffbaaaaffc * Output: a:4 b:1 f:2 c:1 * * Input: bbbbbb * Output: b:6 * * Input: abc * Output: a:1 b:1 c:1 * * Input: aabbcc * Output: a:2 b:2 c:2 * * Input: aaabbbccc * Output: a:3 b:3 c:3 * * Input: a * Output: a:1 * * Input: "" * Output: */