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@@ -0,0 +1,37 @@
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+func isValidSerialization(preorder string) bool {
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+ tree := strings.Split(preorder, ",")
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+ n := len(tree)
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+ if n == 0 || (n == 1 && tree[0] != "#") || (tree[0] == "#" && 1 < n) {
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+ return false
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+ }
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+ st := []int{-1} // 0 for left, and 1 for right
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+ l, i, next := 1, 1, 0
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+ for ; i < n && l != 0; i++ {
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+ if next == 0 {
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+ st = append(st, 0)
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+ l++
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+ if tree[i] == "#" {
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+ next = 1
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+ }
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+ } else {
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+ if tree[i] == "#" {
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+ l--
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+ st = st[:l]
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+ for 2 < l && st[l-1] == 1 {
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+ l--
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+ if st[l-1] != 0 {
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+ return false
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+ }
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+ l--
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+ st = st[:l]
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+ }
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+ } else {
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+ st = append(st, 1)
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+ l++
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+ next = 0
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+ }
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+ }
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+ }
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+ return len(st) == 1 && i == n
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+}
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+
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