word break

Author: se6816

word-break/se6816.java

@@ -0,0 +1,120 @@
+/**
+    Tries 자료구조를 구현하고, 이를 통해 단어를 탐색하는 방식
+    visited[] 방문 배열을 추가하여, 이전에 방문했던 인덱스에 대해서는 무시
+ */
+class WordMap {
+    public Map<Character, WordNode> wordMap;
+
+    public WordMap() {
+        wordMap = new HashMap<>();
+    }
+
+    public List<Integer> search(String word, int idx) {
+        List<Integer> idxList = new ArrayList<>();
+
+        WordNode wordNode = null;
+        char ch = word.charAt(idx);
+        wordNode = wordMap.get(ch);
+        if (wordNode == null) return idxList;
+
+        if(wordNode.isLeaf) {
+            idxList.add(idx + 1);
+        }
+        idx++;
+
+        for(; idx < word.length(); idx++) {
+            char target = word.charAt(idx);
+            if (!wordNode.next.containsKey(target)) {
+                break;
+            }
+            wordNode = wordNode.next.get(target);
+            if (wordNode.isLeaf) {
+                idxList.add(idx + 1);  
+            }
+        }
+
+        return idxList;
+    }
+
+    public void add(String word) {
+        WordNode wordNode = null;
+        char ch = word.charAt(0);
+        wordNode = wordMap.get(ch);
+
+        if(wordNode == null) {
+            boolean isFirstWord = word.length() == 1;
+            wordNode = new WordNode(ch, isFirstWord);
+            wordMap.put(ch, wordNode);
+        }
+
+        for(int idx = 1; idx < word.length(); idx++) {
+            char target = word.charAt(idx);
+            boolean isLeaf = word.length() - 1 == idx;
+            wordNode = wordNode.next.computeIfAbsent(target, key -> new WordNode(key, isLeaf));
+        }
+
+        wordNode.isLeaf = true;
+
+    }
+
+}
+
+class WordNode {
+    char ch;
+    Map<Character, WordNode> next;
+    boolean isLeaf;
+
+    public WordNode(char ch) {
+        this(ch, false);
+    }
+    
+    public WordNode(char ch, boolean isLeaf) {
+        next = new HashMap<>();
+        this.ch = ch;
+        this.isLeaf = isLeaf;
+    }
+
+}
+
+class Solution {
+    public static WordMap wordMap;
+    public boolean wordBreak(String s, List<String> wordDict) {
+        boolean[] visited = new boolean[s.length()];
+        initWordMap(wordDict);
+        if(s.length() == 1) return wordMap.wordMap.containsKey(s.charAt(0)) && wordMap.wordMap.get(s.charAt(0)).isLeaf;
+
+        Queue<Integer> que = new LinkedList<>();
+        boolean result = false;
+        que.add(0);
+        visited[0] = true;
+        loop:
+        while(!que.isEmpty()) {
+            int idx = que.poll();
+            List<Integer> idxList = wordMap.search(s, idx);
+            for(int i : idxList) {
+                if(i == s.length()) {
+                    result = true;
+                    break loop;
+                }
+
+                if(!visited[i]) {
+                    que.add(i);
+                    visited[i] = true;
+                }
+            }
+        }
+
+        return result;
+
+
+
+    }
+    
+    public void initWordMap(List<String> wordDict) {
+        wordMap = new WordMap();
+        for(String word : wordDict) {
+            wordMap.add(word);
+        }
+    }
+}
+