Create 1719-number-of-ways-to-reconstruct-a-tree.js

Author: everthis

1719-number-of-ways-to-reconstruct-a-tree.js

@@ -0,0 +1,132 @@
+class PriorityQueue {
+  constructor(comparator = (a, b) => a > b) {
+    this.heap = []
+    this.top = 0
+    this.comparator = comparator
+  }
+  size() {
+    return this.heap.length
+  }
+  isEmpty() {
+    return this.size() === 0
+  }
+  peek() {
+    return this.heap[this.top]
+  }
+  push(...values) {
+    values.forEach((value) => {
+      this.heap.push(value)
+      this.siftUp()
+    })
+    return this.size()
+  }
+  pop() {
+    const poppedValue = this.peek()
+    const bottom = this.size() - 1
+    if (bottom > this.top) {
+      this.swap(this.top, bottom)
+    }
+    this.heap.pop()
+    this.siftDown()
+    return poppedValue
+  }
+  replace(value) {
+    const replacedValue = this.peek()
+    this.heap[this.top] = value
+    this.siftDown()
+    return replacedValue
+  }
+
+  parent = (i) => ((i + 1) >>> 1) - 1
+  left = (i) => (i << 1) + 1
+  right = (i) => (i + 1) << 1
+  greater = (i, j) => this.comparator(this.heap[i], this.heap[j])
+  swap = (i, j) => ([this.heap[i], this.heap[j]] = [this.heap[j], this.heap[i]])
+  siftUp = () => {
+    let node = this.size() - 1
+    while (node > this.top && this.greater(node, this.parent(node))) {
+      this.swap(node, this.parent(node))
+      node = this.parent(node)
+    }
+  }
+  siftDown = () => {
+    let node = this.top
+    while (
+      (this.left(node) < this.size() && this.greater(this.left(node), node)) ||
+      (this.right(node) < this.size() && this.greater(this.right(node), node))
+    ) {
+      let maxChild =
+        this.right(node) < this.size() &&
+        this.greater(this.right(node), this.left(node))
+          ? this.right(node)
+          : this.left(node)
+      this.swap(node, maxChild)
+      node = maxChild
+    }
+  }
+}
+/**
+ * @param {number[][]} pairs
+ * @return {number}
+ */
+const checkWays = function (pairs) {
+  const adj = {}
+  for (let i = 0; i < pairs.length; i++) {
+    if (adj[pairs[i][0]] == null) adj[pairs[i][0]] = new Set()
+    if (adj[pairs[i][1]] == null) adj[pairs[i][1]] = new Set()
+    adj[pairs[i][0]].add(pairs[i][1])
+    adj[pairs[i][1]].add(pairs[i][0])
+  }
+
+  const q = new PriorityQueue((a, b) => a[0] < b[0])
+  Object.keys(adj).forEach((k) => {
+    q.push([-adj[k].size, +k])
+  })
+
+  const n = q.size()
+  let multiple = false
+  const seen = new Set()
+  while (!q.isEmpty()) {
+    let [sz, v] = q.peek()
+    q.pop()
+    sz = -sz
+    let u = 0
+    let usz = n + 1
+    if (seen.size) {
+      for (let x of adj[v]) {
+        if (adj[x].size < usz && seen.has(x)) {
+          u = x
+          usz = adj[x].size
+        }
+      }
+    }
+
+    seen.add(v)
+    if (u === 0) {
+      if (sz !== n - 1) {
+        return 0
+      }
+      continue
+    }
+
+    for (let x of adj[v]) {
+      if (x == u) {
+        continue
+      }
+
+      if (!adj[u].has(x)) {
+        return 0
+      }
+    }
+
+    if (usz == sz) {
+      multiple = true
+    }
+  }
+
+  if (multiple) {
+    return 2
+  }
+
+  return 1
+}