Create 1489-find-critical-and-pseudo-critical-edges-in-minimum-spanning-tree.js

Author: everthis

1489-find-critical-and-pseudo-critical-edges-in-minimum-spanning-tree.js

@@ -0,0 +1,69 @@
+/**
+ * @param {number} n
+ * @param {number[][]} edges
+ * @return {number[][]}
+ */
+const findCriticalAndPseudoCriticalEdges = function (n, edges) {
+  const criticalEdges = [],
+    psuedoCriticalEdges = [],
+    map = new Map()
+  edges.forEach((edge, i) => map.set(edge, i))
+  edges.sort((a, b) => a[2] - b[2])
+  const buildMST = (pick, skip) => {
+    const uf = new UnionFind(n)
+    let cost = 0
+    if (pick !== null) {
+      uf.union(pick[0], pick[1])
+      cost += pick[2]
+    }
+    for (let edge of edges) {
+      if (edge !== skip && uf.union(edge[0], edge[1])) cost += edge[2]
+    }
+    return uf.count === 1 ? cost : Number.MAX_SAFE_INTEGER
+  }
+  const minCost = buildMST(null, null)
+  for (let edge of edges) {
+    const index = map.get(edge)
+    const costWithout = buildMST(null, edge)
+    if (costWithout > minCost) {
+      criticalEdges.push(index)
+    } else {
+      const costWith = buildMST(edge, null)
+      if (costWith === minCost) psuedoCriticalEdges.push(index)
+    }
+  }
+  return [criticalEdges, psuedoCriticalEdges]
+}
+class UnionFind {
+  constructor(n) {
+    this.parents = Array(n)
+      .fill(0)
+      .map((e, i) => i)
+    this.ranks = Array(n).fill(0)
+    this.count = n
+  }
+  root(x) {
+    while (x !== this.parents[x]) {
+      this.parents[x] = this.parents[this.parents[x]]
+      x = this.parents[x]
+    }
+    return x
+  }
+  find(x) {
+    return this.root(x)
+  }
+  union(x, y) {
+    const [rx, ry] = [this.find(x), this.find(y)]
+    if (this.ranks[rx] >= this.ranks[ry]) {
+      this.parents[ry] = rx
+      this.ranks[rx] += this.ranks[ry]
+    } else if (this.ranks[ry] > this.ranks[rx]) {
+      this.parents[rx] = ry
+      this.ranks[ry] += this.ranks[rx]
+    }
+    if (rx !== ry) {
+      this.count--
+      return true
+    } else return false
+  }
+}