diff --git a/5.leetcode/src/com/fanxb/common/Q127.java b/5.leetcode/src/com/fanxb/common/Q127.java
new file mode 100644
index 0000000..239137e
--- /dev/null
+++ b/5.leetcode/src/com/fanxb/common/Q127.java
@@ -0,0 +1,50 @@
+package com.fanxb.common;
+
+import java.util.*;
+
+public class Q127 {
+    public int ladderLength(String beginWord, String endWord, List<String> wordList) {
+        Set<String> set = new HashSet<>(wordList);
+        Set<String> cache = new HashSet<>();
+        if (!set.contains(endWord)) return 0;
+        Queue<String> queue = new LinkedList<>();
+        queue.offer(beginWord);
+        cache.add(beginWord);
+        int res = Integer.MAX_VALUE;
+        int step = 1;
+        while (!queue.isEmpty()) {
+            int size = queue.size();
+            step++;
+            while (size-- > 0) {
+                String str = queue.poll();
+                boolean continueQueue = false;
+                for (int i = 0; i < str.length(); i++) {
+                    for (int j = 0; j < 26; j++) {
+                        char c = (char) ('a' + j);
+                        if (c != str.charAt(i)) {
+                            StringBuilder builder = new StringBuilder(str);
+                            builder.setCharAt(i, c);
+                            String newStr = builder.toString();
+                            if (!set.contains(newStr) || cache.contains(newStr)) {
+                                continue;
+                            }
+                            if (endWord.equals(newStr)) {
+                                res = Math.min(res, step);
+                                continueQueue = true;
+                                break;
+                            }
+                            cache.add(newStr);
+                            queue.add(newStr);
+                        }
+                    }
+                    if (continueQueue) break;
+                }
+            }
+        }
+        return res == Integer.MAX_VALUE ? 0 : res;
+    }
+
+    public static void main(String[] args) {
+        new Q127().ladderLength("hot", "dog", Arrays.asList("hot", "dog"));
+    }
+}
diff --git a/5.leetcode/src/com/fanxb/common/Q208.java b/5.leetcode/src/com/fanxb/common/Q208.java
new file mode 100644
index 0000000..63245a0
--- /dev/null
+++ b/5.leetcode/src/com/fanxb/common/Q208.java
@@ -0,0 +1,54 @@
+package com.fanxb.common;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+public class Q208 {
+
+    private class Trie {
+
+        private boolean isEnd;
+        private Trie[] child;
+
+
+        public Trie() {
+            isEnd = false;
+            child = new Trie[26];
+        }
+
+        public void insert(String word) {
+            Trie root = this;
+            for (int i = 0; i < word.length(); i++) {
+                int index = word.charAt(i) - 'a';
+                if (root.child[index] == null) {
+                    Trie trie = new Trie();
+                    root.child[index] = trie;
+                }
+                root = root.child[index];
+            }
+            root.isEnd = true;
+        }
+
+
+        public boolean search(String word) {
+            Trie trie = searchRes(word);
+            return trie != null && trie.isEnd;
+        }
+
+        private Trie searchRes(String word) {
+            Trie root = this;
+            for (char c : word.toCharArray()) {
+                int index = c - 'a';
+                if (root.child[index] == null) return null;
+                root = root.child[index];
+            }
+            return root;
+        }
+
+        public boolean startsWith(String prefix) {
+            return searchRes(prefix) != null;
+        }
+    }
+}
diff --git a/5.leetcode/src/com/fanxb/common/Q210.java b/5.leetcode/src/com/fanxb/common/Q210.java
new file mode 100644
index 0000000..80d50df
--- /dev/null
+++ b/5.leetcode/src/com/fanxb/common/Q210.java
@@ -0,0 +1,34 @@
+package com.fanxb.common;
+
+import java.util.*;
+
+public class Q210 {
+    public int[] findOrder(int numCourses, int[][] prerequisites) {
+        //课程入度统计
+        int[] courseCount = new int[numCourses];
+        //记录一门课上完以后接着可以上哪些课
+        Map<Integer, List<Integer>> nextCourseMap = new HashMap<>(numCourses);
+        for (int i = 0; i < prerequisites.length; i++) {
+            int[] temp = prerequisites[i];
+            courseCount[temp[0]]++;
+            nextCourseMap.computeIfAbsent(temp[1], k -> new ArrayList<>()).add(temp[0]);
+        }
+        Queue<Integer> queue = new LinkedList<>();
+        for (int i = 0; i < courseCount.length; i++) {
+            if (courseCount[i] == 0) queue.offer(i);
+        }
+        int[] res = new int[numCourses];
+        int count = 0;
+        while (!queue.isEmpty()) {
+            Integer course = queue.poll();
+            res[count++] = course;
+            nextCourseMap.getOrDefault(course, new ArrayList<>(0)).forEach(item -> {
+                courseCount[item]--;
+                if (courseCount[item] == 0) {
+                    queue.offer(item);
+                }
+            });
+        }
+        return count == numCourses ? res : new int[0];
+    }
+}
diff --git a/5.leetcode/src/com/fanxb/common/Q211.java b/5.leetcode/src/com/fanxb/common/Q211.java
new file mode 100644
index 0000000..bd74d60
--- /dev/null
+++ b/5.leetcode/src/com/fanxb/common/Q211.java
@@ -0,0 +1,58 @@
+package com.fanxb.common;
+
+import java.util.*;
+import java.util.stream.Stream;
+
+public class Q211 {
+    public static class WordDictionary {
+        boolean isEnd;
+        WordDictionary[] child;
+
+        public WordDictionary() {
+            isEnd = false;
+            child = new WordDictionary[26];
+        }
+
+        public void addWord(String word) {
+            WordDictionary root = this;
+            for (char c : word.toCharArray()) {
+                int index = c - 'a';
+                if (root.child[index] == null) root.child[index] = new WordDictionary();
+                root = root.child[index];
+            }
+            root.isEnd = true;
+        }
+
+        public boolean search(String word) {
+            return dfs(this, word, word.length(), 0);
+        }
+
+        private boolean dfs(WordDictionary node, String word, int length, int index) {
+            if (index == length) return node.isEnd;
+            char c = word.charAt(index);
+            if (c == '.') {
+                for (WordDictionary item : node.child) {
+                    boolean isOk = item != null && dfs(item, word, length, index + 1);
+                    if (isOk) return isOk;
+                }
+            } else {
+                int i = c - 'a';
+                if (node.child[i] != null) return dfs(node.child[i], word, length, index + 1);
+            }
+            return false;
+        }
+    }
+
+    public static void main(String[] args) {
+        Q211.WordDictionary q = new Q211.WordDictionary();
+        q.addWord("bad");
+        q.addWord("dad");
+        q.addWord("mad");
+        q.search("pad");
+        q.search("bad");
+        q.search(".ad");
+        q.search("b..");
+
+    }
+
+}
diff --git a/5.leetcode/src/com/fanxb/common/Q212.java b/5.leetcode/src/com/fanxb/common/Q212.java
new file mode 100644
index 0000000..a242ab2
--- /dev/null
+++ b/5.leetcode/src/com/fanxb/common/Q212.java
@@ -0,0 +1,41 @@
+package com.fanxb.common;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+public class Q212 {
+    public List<String> findWords(char[][] board, String[] words) {
+        Set<String> set = new HashSet<>(List.of(words));
+        List<String> res = new ArrayList<>(words.length);
+        int m = board.length, n = board[0].length;
+        for (int i = 0; i < m; i++) {
+            for (int j = 0; j < n; j++) {
+                int[][] cache = new int[board.length][board[0].length];
+                dfs(set, res, board, "", cache, 0, 0, board.length, board[0].length);
+            }
+        }
+        return res;
+    }
+
+    private void dfs(Set<String> set, List<String> res, char[][] board, String temp, int[][] cache, int i, int j, int m, int n) {
+        if (i < 0 || i >= m || j < 0 || j >= n || temp.length() >= 10) return;
+        if (cache[i][j] == 1) return;
+        char c = board[i][j];
+        cache[i][j] = 1;
+        String newStr = temp + c;
+        if (set.contains(newStr)) {
+            res.add(newStr);
+            set.remove(newStr);
+        }
+        dfs(set, res, board, newStr, cache, i, j - 1, m, n);
+        dfs(set, res, board, newStr, cache, i, j + 1, m, n);
+        dfs(set, res, board, newStr, cache, i - 1, j, m, n);
+        dfs(set, res, board, newStr, cache, i + 1, j, m, n);
+    }
+
+    public static void main(String[] args) {
+        new Q212().findWords(new char[][]{{'o', 'a', 'a', 'n'}, {'e', 't', 'a', 'e'}, {'i', 'h', 'k', 'r'}, {'i', 'f', 'l', 'v'}}, new String[]{"oath", "pea", "eat", "rain"});
+    }
+}
diff --git a/5.leetcode/src/com/fanxb/common/Q433.java b/5.leetcode/src/com/fanxb/common/Q433.java
new file mode 100644
index 0000000..de64402
--- /dev/null
+++ b/5.leetcode/src/com/fanxb/common/Q433.java
@@ -0,0 +1,53 @@
+package com.fanxb.common;
+
+import java.util.*;
+
+public class Q433 {
+    public int minMutation(String startGene, String endGene, String[] bank) {
+        Set<String> bankSet = new HashSet<>(bank.length);
+        bankSet.addAll(Arrays.asList(bank));
+        if (!bankSet.contains(endGene)) return -1;
+        if (startGene.equals(endGene)) return 0;
+        int step = 0;
+        char[] chars = new char[]{'A', 'C', 'G', 'T'};
+        Set<String> cache = new HashSet<>();
+        cache.add(startGene);
+        Queue<String> queue = new LinkedList<>();
+        queue.add(startGene);
+        while (!queue.isEmpty()) {
+            step++;
+            int size = queue.size();
+            while (size-- > 0) {
+                String str = queue.poll();
+                List<String> temp = checkDiff(str, chars, bankSet);
+                for (String one : temp) {
+                    if (one.equals(endGene)) return step;
+                    if (cache.contains(one)) continue;
+                    queue.offer(one);
+                    cache.add(one);
+                }
+            }
+        }
+        return -1;
+    }
+
+    /**
+     * 返回所有的替换情况
+     *
+     * @param str
+     * @param endChar
+     * @return
+     */
+    private List<String> checkDiff(String str, char[] chars, Set<String> bankSet) {
+        List<String> res = new ArrayList<>();
+        for (int i = 0; i < 8; i++) {
+            for (int j = 0; j < 4; j++) {
+                if (str.charAt(i) != chars[j]) {
+                    String temp = str.substring(0, i) + chars[j] + str.substring(i + 1);
+                    if (bankSet.contains(temp)) res.add(temp);
+                }
+            }
+        }
+        return res;
+    }
+}
diff --git a/5.leetcode/src/com/fanxb/common/Q909.java b/5.leetcode/src/com/fanxb/common/Q909.java
new file mode 100644
index 0000000..16df77c
--- /dev/null
+++ b/5.leetcode/src/com/fanxb/common/Q909.java
@@ -0,0 +1,23 @@
+package com.fanxb.common;
+
+import java.util.LinkedList;
+import java.util.Queue;
+
+public class Q909 {
+    //记录走过的格子
+    private int[][] cache;
+    private int res = Integer.MAX_VALUE;
+
+    public int snakesAndLadders(int[][] board) {
+        int n = board.length;
+        Queue<Integer[]> queue = new LinkedList<>();
+        queue.add(new Integer[]{n - 1, 0});
+//        int count
+        while (!queue.isEmpty()) {
+            Integer[] node = queue.poll();
+        }
+        return 0;
+    }
+
+
+}