669.修剪二叉搜索树.md

669.修剪二叉搜索树

/*
 * @lc app=leetcode.cn id=669 lang=typescript
 *
 * [669] 修剪二叉搜索树
 */

// @lc code=start
/**
 * Definition for a binary tree node.
 * class TreeNode {
 *     val: number
 *     left: TreeNode | null
 *     right: TreeNode | null
 *     constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
 *         this.val = (val===undefined ? 0 : val)
 *         this.left = (left===undefined ? null : left)
 *         this.right = (right===undefined ? null : right)
 *     }
 * }
 */
function trimBST(root: TreeNode | null, low: number, high: number): TreeNode | null {}
// @lc code=end

解法 1: 递归

function trimBST(root: TreeNode | null, low: number, high: number): TreeNode | null {
  if (!root) return null
  const dfs = (node: TreeNode | null) => {
    if (!node) return null
    ;(node.left = dfs(node.left)), (node.right = dfs(node.right))
    if (node.val <= high && node.val >= low) {
      return node
    } else if (node.val > high) {
      return node.left
    } else {
      return node.right
    }
  }
  return dfs(root)
}

Case

test.each([
  { input: { root: [1, 0, 2], low: 1, high: 2 }, output: [1, null, 2] },
  { input: { root: [3, 0, 4, null, 2, null, null, 1], low: 1, high: 3 }, output: [3, 2, null, 1] },
])('input: root = $input.root, low = $input.low, high = $input.high', ({ input: { root, low, high }, output }) => {
  expect(trimBST(BinaryTree.deserialize(root), low, high)).toEqual(BinaryTree.deserialize(output))
})