205th Commit

README.md

@@ -201,15 +201,16 @@ Ace Coding Interview with 75 Qs
 [700]: ./src/page-7/700.%20Search%20in%20a%20Binary%20Search%20Tree/searchBST.ts
 [450]: ./src/page-5/450.%20Delete%20Node%20in%20a%20BST/deleteNode.ts
 
-| Graphs - DFS                                                 |                 |        |
-| ------------------------------------------------------------ | --------------- | ------ |
-| 841. Keys and Rooms                                          | [Solution][841] | Medium |
-| 547. Number of Provinces                                     | [Solution][547] | Medium |
-| 1466. Reorder Routes to Make All Paths Lead to the City Zero | Solution        | Medium |
-| 399. Evaluate Division                                       | Solution        | Medium |
+| Graphs - DFS                                                 |                  |        |
+| ------------------------------------------------------------ | ---------------- | ------ |
+| 841. Keys and Rooms                                          | [Solution][841]  | Medium |
+| 547. Number of Provinces                                     | [Solution][547]  | Medium |
+| 1466. Reorder Routes to Make All Paths Lead to the City Zero | [Solution][1466] | Medium |
+| 399. Evaluate Division                                       | Solution         | Medium |
 
 [841]: ./src/page-8/841.%20Keys%20and%20Rooms/canVisitAllRooms.ts
 [547]: ./src/page-6/547.%20Number%20of%20Provinces/findCircleNum.ts
+[1466]: ./src/page-14/1466.%20Reorder%20Routes%20to%20Make%20All%20Paths%20Lead%20to%20the%20City%20Zero/minReorder.ts
 
 | Graphs - BFS                             |          |        |
 | ---------------------------------------- | -------- | ------ |

src/page-14/1466. Reorder Routes to Make All Paths Lead to the City Zero/minReorder.test.ts

@@ -0,0 +1,31 @@
+import { minReorder } from './minReorder';
+
+describe('1466. Reorder Routes to Make All Paths Lead to the City Zero', () => {
+  test('minReorder', () => {
+    expect(
+      minReorder(6, [
+        [0, 1],
+        [1, 3],
+        [2, 3],
+        [4, 0],
+        [4, 5],
+      ]),
+    ).toBe(3);
+
+    expect(
+      minReorder(5, [
+        [1, 0],
+        [1, 2],
+        [3, 2],
+        [3, 4],
+      ]),
+    ).toBe(2);
+
+    expect(
+      minReorder(3, [
+        [1, 0],
+        [2, 0],
+      ]),
+    ).toBe(0);
+  });
+});

src/page-14/1466. Reorder Routes to Make All Paths Lead to the City Zero/minReorder.ts

@@ -0,0 +1,39 @@
+type MinReorder = (n: number, connections: number[][]) => number;
+
+/**
+ * Accepted
+ */
+export const minReorder: MinReorder = (n, connections) => {
+  // Create an adjacency list
+  const graph: Map<number, { to: number; originalDirection: boolean }[]> = new Map();
+
+  // Build the bidirectional graph, noting the original directions
+  for (const [u, v] of connections) {
+    // Ensure both nodes u and v exist in the graph
+    graph.set(u, [...(graph.get(u) ?? []), { to: v, originalDirection: true }]);
+    graph.set(v, [...(graph.get(v) ?? []), { to: u, originalDirection: false }]);
+  }
+
+  let changes = 0;
+  const visited = new Set<number>();
+
+  // DFS function to explore the graph
+  function dfs(node: number) {
+    visited.add(node);
+
+    for (const { to, originalDirection } of graph.get(node) ?? []) {
+      if (!visited.has(to)) {
+        // If the edge is originally directed away from node 0, increment the change count
+        if (originalDirection) changes += 1;
+
+        // Recursively apply DFS on the neighbor
+        dfs(to);
+      }
+    }
+  }
+
+  // Start DFS from node 0
+  dfs(0);
+
+  return changes;
+};