feat: 218. The Skyline Problem : 扫描线

Author: upupming

leetcode/残酷刷题/218. The Skyline Problem.js

@@ -0,0 +1,140 @@
+/**
+ * @param {number[][]} buildings
+ * @return {number[][]}
+ */
+const getSkyline = function (b) {
+  const a = []; const h = new RemovableHeap((a, b) => b - a)
+  for (const [l, r, h] of b) {
+    a.push([l, h, 1])
+    a.push([r, h, -1])
+  }
+  a.sort((x, y) => x[0] - y[0])
+  const ans = []
+  for (let i = 0; i < a.length;) {
+    const x = a[i][0]; let j = i
+    while (j < a.length && a[j][0] === x) {
+      const [_, y, f] = a[j]
+      if (f === -1) h.remove(y)
+      else h.push(y)
+      j++
+    }
+    i = j
+    const cur = h.top() ?? 0
+    if (!ans.length || ans[ans.length - 1][1] !== cur) {
+      ans.push([x, cur])
+    }
+  }
+  return ans
+}
+
+class Heap {
+  constructor (data = [], compare = (lhs, rhs) => lhs < rhs ? -1 : lhs > rhs ? 1 : 0) {
+    if (typeof data === 'function') {
+      compare = data
+      data = []
+    }
+    this.data = [null, ...data]
+    this.lt = (i, j) => compare(this.data[i], this.data[j]) < 0
+    for (let i = this.size(); i > 0; i--) { this.heapify(i) }
+  }
+
+  size () {
+    return this.data.length - 1
+  }
+
+  push (v) {
+    this.data.push(v)
+    let i = this.size()
+    while (i >> 1 !== 0 && this.lt(i, i >> 1)) { this.swap(i, i >>= 1) }
+  }
+
+  pop () {
+    this.swap(1, this.size())
+    const top = this.data.pop()
+    this.heapify(1)
+    return top
+  }
+
+  top () {
+    return this.data[1]
+  }
+
+  heapify (i) {
+    while (true) {
+      let min = i
+      const [l, r, n] = [i * 2, i * 2 + 1, this.data.length]
+      if (l < n && this.lt(l, min)) { min = l }
+      if (r < n && this.lt(r, min)) { min = r }
+      if (min !== i) {
+        this.swap(i, min)
+        i = min
+      } else { break }
+    }
+  }
+
+  clear () {
+    this.data = [null]
+  }
+
+  swap (i, j) {
+    const d = this.data;
+    [d[i], d[j]] = [d[j], d[i]]
+  }
+}
+
+class RemovableHeap {
+  constructor (data = [], cmp) {
+    this.heap = new Heap(data, cmp)
+    this.counts = new Map()
+    this._invalidCount = 0
+    for (let i = 1; i < this.heap.data.length; i++) {
+      this._setCount(this.heap.data[i], 1)
+    }
+  }
+
+  size () {
+    return this.heap.size() - this._invalidCount
+  }
+
+  top () {
+    this._normalize()
+    return this.heap.top()
+  }
+
+  pop () {
+    this._normalize()
+    if (this.heap.size() < 1) { return void 0 }
+    const top = this.heap.pop()
+    this._setCount(top, -1)
+    return top
+  }
+
+  push (num) {
+    this._setCount(num, 1)
+    this.heap.push(num)
+  }
+
+  remove (num) {
+    if (Number(this.counts.get(num)) > 0) {
+      this._setCount(num, -1)
+      this._invalidCount++
+    }
+  }
+
+  has (value) {
+    return this.counts.get(value) > 0
+  }
+
+  _setCount (num, diff) {
+    let _a
+    const count = (_a = this.counts.get(num)) != null ? _a : 0
+    this.counts.set(num, count + diff)
+  }
+
+  _normalize () {
+    while (this.heap.size() && !this.counts.get(this.heap.top())) {
+      this.heap.pop()
+      this._invalidCount--
+    }
+  }
+}

leetcode/残酷刷题/README.md

@@ -273,6 +273,7 @@
 ### 扫描线 (Sweep Line)
 
 - 56. Merge Intervals
+- 218. The Skyline Problem
 
 ## Links