https://leetcode.com/problems/first-unique-character-in-a-string/description/

First non-repeating char position.

https://leetcode.com/problems/group-anagrams/description/

Group words by chars in them.

https://leetcode.com/problems/sort-characters-by-frequency/description

Sort string by char's frequencies.

https://leetcode.com/problems/perfect-squares/description

Min square numbers sum up to n.

https://leetcode.com/problems/largest-divisible-subset/description

Longest subset of divisible by s[i] % s[j] == 0 || s[j] % s[i] == 0.

https://leetcode.com/problems/palindromic-substrings/description/

Count palindromes substrings.

https://leetcode.com/problems/cherry-pickup-ii/description/

Maximum paths sum of two robots top-down in XY grid.

https://leetcode.com/problems/majority-element/description/

Element with frequency > nums.len / 2.

https://leetcode.com/problems/find-first-palindromic-string-in-the-array/description/

Find a palindrome.

https://leetcode.com/problems/rearrange-array-elements-by-sign/description/

Rearrange array to positive-negative sequence.

https://leetcode.com/problems/find-polygon-with-the-largest-perimeter/description/

The largest subset sum(a[..i]) > a[i + 1] where a is a subset of array.

https://leetcode.com/problems/least-number-of-unique-integers-after-k-removals/description

Min uniq count after removing k numbers.

isn't it scary

https://leetcode.com/problems/furthest-building-you-can-reach/description

Max index to climb diff = a[i +1] - a[i] > 0 using bricks -= diff and ladders-- for each.

https://leetcode.com/problems/meeting-rooms-iii/description

Most frequent room of 0..<n where each meeting[i]=[start, end) takes or delays until first available.

https://leetcode.com/problems/power-of-two/description/

Is number 2^x?

Congrats for all the earners!

https://leetcode.com/problems/missing-number/description/

Missing in [0..n] number.

https://leetcode.com/problems/bitwise-and-of-numbers-range/description

Bitwise AND for [left..right].

https://leetcode.com/problems/find-the-town-judge/description/

Find who trusts nobody and everybody trusts him in [trust, trusted] array.

https://leetcode.com/problems/cheapest-flights-within-k-stops/description/

Cheapest travel src -> dst with at most k stops in a directed weighted graph.