1110.删点成林.md

1110.删点成林

/*
 * @lc app=leetcode.cn id=1110 lang=typescript
 *
 * [1110] 删点成林
 */

// @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 delNodes(root: TreeNode | null, to_delete: number[]): Array<TreeNode | null> {}
// @lc code=end

解法 1: dfs

function delNodes(root: TreeNode | null, to_delete: number[]): Array<TreeNode | null> {
  if (!root) return []
  const res: Array<TreeNode | null> = [],
    set = new Set(to_delete)
  const dfs = (node: TreeNode | null) => {
    if (!node) return true
    const ans = set.has(node.val)
    for (let child of ['left', 'right']) {
      if (!node[child]) continue
      if (dfs(node[child])) {
        node[child] = null
      } else {
        if (ans) res.push(node[child])
      }
    }

    return ans
  }
  if (!dfs(root)) res.push(root)
  return res
}

Case

test.each([
  { input: { root: [1, 2, 3, 4, 5, 6, 7], to_delete: [3, 5] }, output: [[1, 2, null, 4], [6], [7]] },
  { input: { root: [1, 2, 4, null, 3], to_delete: [3] }, output: [[1, 2, 4]] },
])('input: root = $input.root, to_delete = $input.to_delete', ({ input: { root, to_delete }, output }) => {
  expect(delNodes(BinaryTree.deserialize(root), to_delete).sort((a, b) => a!.val - b!.val)).toEqual(
    output.map(BinaryTree.deserialize).sort((a, b) => a!.val - b!.val),
  )
})