https://leetcode.com/problems/isomorphic-strings/description/

Can map chars from one string to another? #easy

https://leetcode.com/problems/word-search/description/

Does grid have a word path? #medium

https://leetcode.com/problems/maximum-nesting-depth-of-the-parentheses/description/

Max nested parenthesis #easy

https://leetcode.com/problems/make-the-string-great/description/

Remove lowercase-uppercase pairs #easy

https://leetcode.com/problems/minimum-remove-to-make-valid-parentheses/description/

Remove minimum to make parenthesis valid #medium

https://leetcode.com/problems/valid-parenthesis-string/description/

Are parenthesis valid with wildcard? #medium

https://leetcode.com/problems/number-of-students-unable-to-eat-lunch/description/

First sandwitch not eaten by any while popped from a queue #easy

https://leetcode.com/problems/time-needed-to-buy-tickets/description/

Seconds to buy tickets by k-th person in a rotating 1 second queue #easy

Congrats for all passing 100 Days💯

https://leetcode.com/problems/reveal-cards-in-increasing-order/description/

Sort cards by rules: take top, next goes bottom #medium

https://leetcode.com/problems/remove-k-digits/description/

Minimum number after removing k digits #medium

https://leetcode.com/problems/trapping-rain-water/description/

Trap the water in area between vertical walls #hard

https://leetcode.com/problems/maximal-rectangle/description/

Max 1-only area in a 0-1 matrix #hard

https://leetcode.com/problems/sum-of-left-leaves/description/

Left-leaf sum in a Binary Tree #easy

https://leetcode.com/problems/sum-root-to-leaf-numbers/description/

Sum root-leaf numbers in a Binary Tree #medium

https://leetcode.com/problems/add-one-row-to-tree/description/

Insert nodes at the depth of the Binary Tree #medium

https://leetcode.com/problems/smallest-string-starting-from-leaf/description/

Smallest string from leaf to root in a Binary Tree #medium

https://leetcode.com/problems/island-perimeter/description/

Perimeter of 1's islands in 01-matrix #easy

https://leetcode.com/problems/number-of-islands/description/

Count 1-islands in 0-1 a 2D matrix #medium

https://leetcode.com/problems/find-all-groups-of-farmland/description/

Count 1-rectangles in 0-1 2D matrix #medium

https://leetcode.com/problems/find-if-path-exists-in-graph/description/

Are source and destination connected in graph? #easy