LeetCode

988. Smallest String Starting From Leaf

find the lexicographically smallest string starting from the leaf to root node

LeetCode

129. Sum Root to Leaf Numbers

Sum of paths from root to leaf

LeetCode

404. Sum of Left Leaves

Sum of Left Leaves of a binary tree.

LeetCode

405. Convert a Number to Hexadecimal

Convert a decimal number to hexadecimal.

LeetCode

623. Add One Row to Tree

Insert a layer to a binary tree.