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top-100-liked/44/leetcode_test.go

@@ -0,0 +1,30 @@
+package top100liked
+
+// https://leetcode.cn/problems/kth-smallest-element-in-a-bst/description/?envType=study-plan-v2&envId=top-100-liked
+
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+func kthSmallest(root *TreeNode, k int) int {
+	res, cnt := 0, 0
+	var helper func(node *TreeNode) bool
+	helper = func(node *TreeNode) bool {
+		if node == nil {
+			return false
+		}
+		if helper(node.Left) {
+			return true
+		}
+		cnt++
+		if cnt == k {
+			res = node.Val
+			return true
+		}
+		return helper(node.Right)
+	}
+	helper(root)
+	return res
+}