Create LongestStringChain.java

Author: Foxeyyy

LongestStringChain.java

@@ -0,0 +1,59 @@
+class Solution {
+
+    public int longestStrChain(String[] words) {
+        
+        List<List<Integer>> paths = buildGraph(words);
+        
+        int[] scores = new int[words.length];
+        int maximumLength = 0;
+        
+        for(int i = 0; i < words.length; i++) {
+            maximumLength = Math.max(maximumLength, longest(i, scores, paths));
+        }
+        
+        return maximumLength;
+        
+    }
+    
+    private List<List<Integer>> buildGraph(String[] words) {
+        List<List<Integer>> paths = new ArrayList<>(words.length);
+        Map<String, Integer> wordIdx = new HashMap<>();
+        
+        for (int i = 0; i < words.length; i++) {
+            paths.add(new LinkedList<>());
+            wordIdx.put(words[i], i);
+        }
+        
+        for (int i = 0; i < words.length; i++) {
+            String word = words[i];
+            for(int j = 0; j < word.length(); j++) {
+                String possible = word.substring(0, j) + word.substring(j + 1);
+                
+                if (!wordIdx.containsKey(possible)) continue;
+                
+                int possibleIdx = wordIdx.get(possible);
+                
+                List<Integer> possiblePaths = paths.get(possibleIdx);
+                possiblePaths.add(i);
+                paths.set(possibleIdx, possiblePaths);
+            }
+        }
+        
+        return paths;
+    }
+    
+    private int longest(int v, int[] scores, List<List<Integer>> paths) {
+        if (scores[v] > 0) return scores[v];
+        
+        int longestPath = 1;
+        
+        for(Integer child: paths.get(v)) {
+            longestPath = Math.max(longestPath, longest(child, scores, paths) + 1);
+        }
+        
+        scores[v] = longestPath;
+        
+        return longestPath;
+    }
+    
+}