feat(book/pq): add exercise with pq and dijkstra

book/interview-questions/network-delay-time.js

@@ -1,28 +1,57 @@
-// https://leetcode.com/problems/network-delay-time/solution/
-function networkDelayTime(times: number[][], N: number, K: number): number {
-  const graph = new Map<number, [number, number][]>(Array(N).fill(0).map((_, i) => [i + 1, []]));
-  times.forEach(([u, v, w]) => graph.get(u)?.push([v, w]));
+const { PriorityQueue, Queue } = require('../../src/index');
 
-  const queue = new Queue([[K, 0]]);
-  const seen = Array(N + 1).fill(Infinity);
+// tag::description[]
+function networkDelayTime(times, N, K) {
+  // end::description[]
+  // tag::placeholder[]
+  // write your code here...
+  // end::placeholder[]
+  // tag::solution[]
+  const graph = new Map(Array(N).fill(0).map((_, i) => [i + 1, []]));
+  times.forEach(([u, v, w]) => graph.get(u).push([v, w]));
 
-  while (queue.size()) {
-    const [node, dist] = queue.dequeue();
-    seen[node] = Math.min(seen[node], dist);
+  const q = new PriorityQueue([[0, K]]);
+  const dist = new Map();
 
-    for (const [adj, w] of graph.get(node) || []) {
-      if (seen[adj] > dist + w) queue.enqueue([adj, dist + w]);
+  while (q.size) {
+    const [d, n] = q.dequeue();
+
+    if (dist.has(n)) continue;
+    dist.set(n, d);
+
+    for (const [adj, w] of graph.get(n)) {
+      if (!dist.has(adj)) q.enqueue([d + w, adj]);
     }
   }
 
-  const max = Math.max(...seen.slice(1));
-  return max === Infinity ? -1 : max;
-};
+  return dist.size === N ? Math.max(...dist.values()) : -1;
+  // end::solution[]
+  // tag::description[]
+}
+// end::description[]
+
+// tag::networkDelayTimeQueue[]
+function networkDelayTimeQueue(times, N, K) {
+  const graph = new Map(Array(N).fill(0).map((_, i) => [i + 1, []]));
+  times.forEach(([u, v, w]) => graph.get(u).push([v, w]));
+
+  const q = new Queue([[0, K]]);
+  const dist = new Map();
 
-/*
-[[2,1,1],[2,3,1],[3,4,1]]
-4
-2
+  while (q.size) {
+    const [d, n] = q.dequeue();
+
+    dist.set(n, dist.has(n) ? Math.min(dist.get(n), d) : d);
+
+    for (const [adj, w] of graph.get(n)) {
+      if (!dist.has(adj) || dist.get(adj) > d + w) {
+        q.enqueue([d + w, adj]);
+      }
+    }
+  }
 
+  return dist.size === N ? Math.max(...dist.values()) : -1;
+}
+// end::networkDelayTimeQueue[]
 
-*/
+module.exports = { networkDelayTime, networkDelayTimeQueue };