solves #433: Minimum Genetic Mutation in java

Author: anishLearnsToCode

README.md

@@ -317,6 +317,7 @@
 | 422  | 🔒 [Valid Word Square](https://leetcode.com/problems/valid-word-square)                                                                                                |                                                                                                                                                                                                                                  |                                                                                                                                   |
 | 429  | 🔒 [N-ary Tree Level Order Traversal](https://leetcode.com/problems/n-ary-tree-level-order-traversal)                                                                  |                                                                                 [![Java](assets/java.png)](src/NAryTreeLevelOrderTraversal.java)                                                                                 |                                                                                                                                   |
 | 430  | [Flatten a Multilevel Doubly Linked List](https://leetcode.com/problems/flatten-a-multilevel-doubly-linked-list)                                                       |                                                                             [![Java](assets/java.png)](src/FlattenAMultiLevelDoublyLinkedList.java)                                                                              |                                                                                                                                   |
+| 433  | [Minimum Genetic Mutation](https://leetcode.com/problems/minimum-genetic-mutation)                                                                                     |                                                                                   [![Java](assets/java.png)](src/MinimumGeneticMutation.java)                                                                                    |                                                                                                                                   |
 | 434  | [Number of Segments in a String](https://leetcode.com/problems/number-of-segments-in-a-string)                                                                         |                                              [![Java](assets/java.png)](src/NumberOfSegmentsInString.java) [![Python](assets/python.png)](python/number_of_segments_in_a_string.py)                                              |                                                                                                                                   |
 | 441  | [Arranging Coins](https://leetcode.com/problems/arranging-coins)                                                                                                       |                                                          [![Java](assets/java.png)](src/ArrangingCoins.java) [![Python](assets/python.png)](python/arranging_coins.py)                                                           |                                                                                                                                   |
 | 443  | [String Compression](https://leetcode.com/problems/string-compression)                                                                                                 |                                                       [![Java](assets/java.png)](src/StringCompression.java) [![Python](assets/python.png)](python/string_compression.py)                                                        |                                                                                                                                   |

src/MinimumGeneticMutation.java

@@ -0,0 +1,66 @@
+// https://leetcode.com/problems/minimum-genetic-mutation
+// T: O(B)
+// S: O(1)
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Map;
+import java.util.Queue;
+import java.util.Set;
+
+public class MinimumGeneticMutation {
+    private record Info(String mutation, int steps) {}
+
+    private static final char[] GENES = new char[] {'A', 'G', 'C', 'T'};
+
+    // n = length of string (8), m = possible number of characters
+    // BFS, T: O(V + E) = O(nB + n^m * mn) S: O(n^m)
+    public static int minMutation(String startGene, String endGene, String[] bank) {
+        final Set<String> genePool = toSet(bank);
+        if (!genePool.contains(endGene)) {
+            return -1;
+        }
+
+        final Queue<Info> queue = new LinkedList<>() {{ add(new Info(startGene, 0)); }};
+        final Map<String, Integer> distances = new HashMap<>();
+
+        while (!queue.isEmpty()) {
+            final Info info = queue.poll();
+            if (distances.getOrDefault(info.mutation, Integer.MAX_VALUE) <= info.steps) {
+                continue;
+            }
+            distances.put(info.mutation, info.steps);
+
+            for (String neighbour : validMutations(genePool, info.mutation)) {
+                queue.add(new Info(neighbour, info.steps + 1));
+            }
+        }
+
+        return distances.getOrDefault(endGene, -1);
+    }
+
+    // T: O(|s|), S: O(|s|)
+    private static List<String> validMutations(Set<String> genePool, String s) {
+        final List<String> result = new ArrayList<>();
+        for (int i = 0 ; i < s.length() ; i++) {
+            for (char c : GENES) {
+                final String mutation = s.substring(0, i) + c + s.substring(i + 1);
+                if (genePool.contains(mutation)) {
+                    result.add(mutation);
+                }
+            }
+        }
+        return result;
+    }
+
+    // T: O(nB) S: O(nB)
+    private static Set<String> toSet(String[] bank) {
+        final Set<String> set = new HashSet<>();
+        Collections.addAll(set, bank);
+        return set;
+    }
+}