Member Avatar for jam7cacci

Just wanna have it checked if i'm doing this rightly...

i was given an expression to translate it into a polish notation and traversals.

the expression is

{( a + b ) - c } * { d * (e / f + g)}

here's my answer:

POSTFIX : a b + c - d e f g + / * *
PREFIX : * - + a b c * d / e + f g

PRE-ORDER : * - + a c b * d / e + f g
POST-ORDER: a b + c - f g + e / d * *
IN-ORDER : a + b - c * d * e / f + g

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Key point: prefix (Polish) is the preorder of the expression tree (visit node, then left, then right), and postfix (reverse Polish) is the postorder (left, right, then node). was right to flag a mismatch — if prefix and a preorder traversal differ, the expression tree or the traversal order is wrong. Common causes are mis-parsed parentheses, incorrect operator precedence, or swapped left/right children when building the tree.

A short verification workflow:

  1. Parse the infix expression into a binary expression tree respecting parentheses and operator precedence (or use the shunting-yard algorithm to get postfix reliably).
  2. Produce prefix by a preorder walk (emit the node before its children) and postfix by a postorder walk (emit after children).
  3. For infix (inorder) output, emit parentheses around each operator node to preserve grouping; plain inorder without parentheses is ambiguous and will usually not match the original grouping.
    To test results, evaluate the original infix and the converted prefix/postfix with a few numeric substitutions — matching numeric results confirm correctness.

Troubleshooting tips: draw the tree and confirm left/right child order, check each parenthesis pair during parsing, and compare a shunting-yard-produced postfix with the postorder output. Helpful references: Polish notation, Tree traversal, Shunting-yard algorithm. , the corrections you made look like progress; focus next on tree construction and adding parentheses for inorder.

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Member Avatar for thoughtcoder

No, you aren't.

Member Avatar for jam7cacci

No, you aren't.

awww... :(

can you please help me understand this?

Member Avatar for thoughtcoder

Why is your prefix notation and preorder traversal any different?

Member Avatar for jam7cacci

Why is your prefix notation and preorder traversal any different?

:(

that's how i understood it... :(

should they always be the same?

Member Avatar for jam7cacci

i'll try it again

pre-order:
* - + a b c * d / e + f g

post-order:
a b + c - f g + e / d * *

in-order:
a + b - c f + g e / d * *

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