Create 2699-modify-graph-edge-weights.js

Author: everthis

2699-modify-graph-edge-weights.js

@@ -0,0 +1,146 @@
+class PQ {
+  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} n
+ * @param {number[][]} edges
+ * @param {number} source
+ * @param {number} destination
+ * @param {number} target
+ * @return {number[][]}
+ */
+const modifiedGraphEdges = function (n, edges, source, destination, target) {
+  const kMax = Number.MAX_SAFE_INTEGER
+  const graph = Array(n)
+    .fill(null)
+    .map(() => [])
+
+  for (const [u, v, w] of edges) {
+    if (w === -1) {
+      continue
+    }
+    graph[u].push([v, w])
+    graph[v].push([u, w])
+  }
+
+  const distToDestination = dijkstra(graph, source, destination)
+  if (distToDestination < target) {
+    return []
+  }
+  if (distToDestination === target) {
+    // Change the weights of negative edges to an impossible value.
+    for (const edge of edges) {
+      if (edge[2] === -1) {
+        edge[2] = kMax
+      }
+    }
+    return edges
+  }
+
+  for (let i = 0; i < edges.length; i++) {
+    const [u, v, w] = edges[i]
+    if (w !== -1) {
+      continue
+    }
+    edges[i][2] = 1
+    graph[u].push([v, 1])
+    graph[v].push([u, 1])
+    const distToDestination = dijkstra(graph, source, destination)
+    if (distToDestination <= target) {
+      edges[i][2] += target - distToDestination
+      // Change the weights of negative edges to an impossible value.
+      for (let j = i + 1; j < edges.length; j++) {
+        if (edges[j][2] === -1) {
+          edges[j][2] = kMax
+        }
+      }
+      return edges
+    }
+  }
+
+  return []
+}
+
+function dijkstra(graph, src, dst) {
+  const dist = Array(graph.length).fill(Infinity)
+  const minHeap = new PQ((a, b) => a[0] < b[0])
+
+  dist[src] = 0
+  minHeap.push([dist[src], src])
+
+  while (!minHeap.isEmpty()) {
+    const [d, u] = minHeap.pop()
+    for (const [v, w] of graph[u] || []) {
+      if (d + w < dist[v]) {
+        dist[v] = d + w
+        minHeap.push([dist[v], v])
+      }
+    }
+  }
+
+  return dist[dst]
+}