Pretty Sure

LeetCode - Single Element in a Sorted Array

Question Definition

Given a sorted array consisting of only integers where every element appears twice except for one element which appears once. Find this single element that appears only once.

LeetCode - Shuffle an Array

Question Definition

Shuffle a set of numbers without duplicates.

LeetCode - Random Pick Index

Question Definition

Given an array of integers with possible duplicates, randomly output the index of a given target number. You can assume that the given target number must exist in the array.

LeetCode - Magical String

Question Definition

A magical string S consists of only ‘1’ and ‘2’ and obeys the following rules:

The string S is magical because concatenating the number of contiguous occurrences of characters ‘1’ and ‘2’ generates the string S itself.

The first few elements of string S is the following: S = “1221121221221121122……”

If we group the consecutive ‘1’s and ‘2’s in S, it will be:

1 22 11 2 1 22 1 22 11 2 11 22 ……

and the occurrences of ‘1’s or ‘2’s in each group are:

1 2 2 1 1 2 1 2 2 1 2 2 ……

You can see that the occurrence sequence above is the S itself.

Given an integer N as input, return the number of ‘1’s in the first N number in the magical string S.

LeetCode - Longest Repeating Character Replacement

Question Definition

Given a string that consists of only uppercase English letters, you can replace any letter in the string with another letter at most k times. Find the length of a longest substring containing all repeating letters you can get after performing the above operations.