Doubt in max sum path from any node to node

I’m not able to imagine/understand line 120 - 124. I’m not getting why we are doing this and will not able to implement the same myself till I’m not clear with the exact reason.

Hello @gambhirrahul0 we are here calculating max sum of current node we need 4 things

  1. left branch sum
  2. right branch sum
  3. max sum of left subtree
  4. max sum of right subtree
    so we have to call left and right
    each of them will return two things => branch sum and max sum
    Branch sum is sum of path starting from root of left or right subtree to the any node is that subtree

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