https://leetcode.com/problems/number-of-submatrices-that-sum-to-target/description/

Count submatrix target sums.

https://leetcode.com/problems/implement-queue-using-stacks/description

Queue by 2 stacks.

https://leetcode.com/problems/evaluate-reverse-polish-notation/description

Solve Reverse Polish Notation.

https://leetcode.com/problems/daily-temperatures/description/

Array of distances to the next largest.

https://leetcode.com/problems/divide-array-into-arrays-with-max-difference/description

Split array into tripples with at most k difference.

https://leetcode.com/problems/sequential-digits/description

Numbers with sequential digits in low..high range.

https://leetcode.com/problems/partition-array-for-maximum-sum/description/

Max sum of partition array into chunks size of at most k filled with max value in chunk.

777's day of leetcode

https://leetcode.com/problems/minimum-window-substring/description

Minimum window of s including all chars of t.

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.