# LeetCode 1457. Pseudo-Palindromic Paths in a Binary Tree in F#

## URL

leetcode.com/problems/pseudo-palindromic-pa..

## Code

github.com/syohex/dotnet-study/blob/master/..

```
type Tree =
| Leaf
| Node of int * Tree * Tree
let pseudoPalindromicPaths (root: Tree) : int =
let isPseudoPalindrome m =
let odds =
m
|> Map.fold (fun acc _ v -> if v % 2 = 1 then acc + 1 else acc) 0
odds <= 1
let rec pseudoPalindromicPaths' node freq =
match node with
| Leaf -> failwith "never reach here"
| Node (v, left, right) ->
let freq' =
match Map.tryFind v freq with
| None -> Map.add v 1 freq
| Some (x) -> Map.add v (x + 1) freq
match left, right with
| Leaf, Leaf ->
if isPseudoPalindrome freq' then
1
else
0
| Node (_), Leaf -> pseudoPalindromicPaths' left freq'
| Leaf, Node (_) -> pseudoPalindromicPaths' right freq'
| Node (_), Node (_) ->
let left = pseudoPalindromicPaths' left freq'
let right = pseudoPalindromicPaths' right freq'
left + right
pseudoPalindromicPaths' root Map.empty
```