if the input is [-1,2,-4,-1,-1,111,100,null,null,null,null,1] then the solution incorrectly shows 208 whereas the answer is 209 as the path2-->-1>-4-->(left)111-->1
-->right)100 yield 209

root is -1.. having children 2 and -4, then the next level children are -1,-1,111,100 and the last level has 1 as the left child of 111. Is this understanding wrong?