2471.js

/** ------------------------------------------------------------------------------
 * 
 * 2471. Minimum Number of Operations to Sort a Binary Tree by Level
 * Topics: Tree, BFS
 * https://leetcode.com/problems/minimum-number-of-operations-to-sort-a-binary-tree-by-level/?envType=daily-question&envId=2024-12-23
 * 
 ------------------------------------------------------------------------------ */
/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @return {number}
 */
var minimumOperations = function (root) {
  let curr = [root]
  let answer = 0

  while (curr.length > 0) {
    const size = curr.length
    const treeLevel = curr.map((node) => node.val)
    const sortArr = treeLevel.map((n) => n).sort((a, b) => a - b)

    const map = new Map()

    for (let i = 0; i < size; i++) {
      map.set(sortArr[i], i)
    }

    for (let i = 0; i < size; i++) {
      let j = map.get(treeLevel[i])
      while (i != j) {
        answer++
        let temp = treeLevel[j]
        treeLevel[j] = treeLevel[i]
        treeLevel[i] = temp
        j = map.get(temp)
      }
    }

    let next = []

    for (let i = 0; i < size; i++) {
      let node = curr[i]
      if (node.left) next.push(node.left)
      if (node.right) next.push(node.right)
    }
    curr = next
  }
  return answer
}