How does LeetCode find the smallest element in a binary search tree?
This article mainly introduces how LeetCode finds the smallest element in the binary search tree, which is very detailed and has a certain reference value. Friends who are interested must read it!
1. Brief introduction of the problem.
Given a binary search tree, write a function kthSmallest to find the k smallest element in it.
Explanation: you can assume that k is always valid, 1 ≤ k ≤ binary search tree number of elements.
2, example
Example 1:
Input: root = [3Person1Magol 4jnullMagne2], k = 1 3 /\ 1 4\ 2 output: 1 example 2:
Input: root = [5, 3, 6, 6, 2, 4, and 4], k = 3 5 /\ 3 6 /\ 2 4 / 1 output: 3.
3, the train of thought of solving the problem
Use the middle order traversal method of binary tree to solve the problem.
4, problem solving procedure
Import java.util.ArrayList;import java.util.List
Public class KthSmallestTest3 {public static void main (String [] args) {TreeNode T1 = new TreeNode (3); TreeNode T2 = new TreeNode (1); TreeNode T3 = new TreeNode (4); TreeNode T4 = new TreeNode (2); t1.left = T2; t1.right = T3; t2.right = T4; int k = 1; int kthSmallest = kthSmallest (T1, k) System.out.println ("kthSmallest =" + kthSmallest)
}
Private static List list = new ArrayList ()
Public static int kthSmallest (TreeNode root, int k) {if (root = = null) {return 0;} dfs (root); return list.get (k-1);}
Private static void dfs (TreeNode root) {if (root = = null) {return;} if (root.left! = null) {dfs (root.left)
} list.add (root.val); if (root.right! = null) {dfs (root.right);}
5. Picture version of the problem solving program.
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