Problem - Path Sum

Given the root of a binary tree and an integer targetSum, return true if the tree has a root-to-leaf path such that adding up all values along the path equals targetSum.

A leaf is a node with no children. Example: For tree $[5,4,8,11,null,13,4,7,2,null,null,null,1]$ and target 22, the path $5 \to 4 \to 11 \to 2$ sums to 22. Constraints: up to $5000$ nodes, values from $-1000$ to $1000$, target from $-1000$ to $1000$.