feat: add Keys and Rooms LeetCode problem (#1189)

Co-authored-by: David Leal <halfpacho@gmail.com>

leetcode/DIRECTORY.md

@@ -95,6 +95,7 @@
 | 709  | [To Lower Case](https://leetcode.com/problems/to-lower-case/)                                                                   | [C](./src/709.c)  | Easy       |
 | 771  | [Jewels and Stones](https://leetcode.com/problems/jewels-and-stones/)                                                           | [C](./src/771.c)  | Easy       |
 | 807  | [Max Increase to Keep City Skyline](https://leetcode.com/problems/max-increase-to-keep-city-skyline/description/)               | [C](./src/807.c)  | Medium     |
+| 841  | [Keys and Rooms](https://leetcode.com/problems/keys-and-rooms/description/)                                                     | [C](./src/841.c)  | Medium     |
 | 852  | [Peak Index in a Mountain Array](https://leetcode.com/problems/peak-index-in-a-mountain-array/)                                 | [C](./src/852.c)  | Easy       |
 | 876  | [Middle of the Linked List](https://leetcode.com/problems/middle-of-the-linked-list/)                                           | [C](./src/876.c)  | Easy       |
 | 901  | [Online Stock Span](https://leetcode.com/problems/online-stock-span/)                                                           | [C](./src/901.c)  | Medium     |

leetcode/src/841.c

@@ -0,0 +1,27 @@
+void visitRooms(int key, int** rooms, int roomsSize, int* roomsColSize, int* visitedRooms){
+    if (visitedRooms[key] == 1){
+        return;
+    }
+
+    visitedRooms[key] = 1;
+    for (int i = 0; i < roomsColSize[key]; i++){
+        visitRooms(rooms[key][i], rooms, roomsSize, roomsColSize, visitedRooms);
+    }
+}
+
+// Depth-first search
+// Runtime: O(n)
+// Space: O(n)
+bool canVisitAllRooms(int** rooms, int roomsSize, int* roomsColSize){
+    int* visitedRooms = calloc(roomsSize, sizeof(int));
+    visitRooms(0, rooms, roomsSize, roomsColSize, visitedRooms);
+
+    int visitedRoomsNumber = 0;
+    for (int i = 0; i < roomsSize; i++){
+        if (visitedRooms[i] == 1){
+            visitedRoomsNumber++;
+        }
+    }
+
+    return visitedRoomsNumber == roomsSize;
+}