add 0126

Author: luliyucoordinate

src/0126-Word-Ladder-II/0126.cpp

@@ -0,0 +1,70 @@
+class Solution 
+{
+public:
+    vector<vector<string>> findLadders(string beginWord, string endWord, vector<string> &wordList) 
+    {
+        int step = 2;
+        vector<vector<string>> res;
+        unordered_set<string> wordDict(wordList.begin(), wordList.end());
+        if (wordDict.count(endWord) == 0) return res;
+        unordered_map<string, vector<vector<string>>> s1, s2, stack;
+        s1[beginWord] = {{beginWord}};
+        s2[endWord] = {{endWord}};
+
+        while (!s1.empty())
+        {
+            stack.clear();
+            for (auto s : s1) wordDict.erase(s.first);
+            for (auto s : s1)
+            {
+                for (int i = 0; i < beginWord.size(); ++i)
+                {
+                    for (char c = 'a'; c <= 'z'; ++c)
+                    {
+                        string tmp = s.first;
+                        tmp[i] = c;
+                        if (!wordDict.count(tmp)) continue;
+                        if (s2.count(tmp)) 
+                        {
+                            if (s.second[0][0] == beginWord)
+                            {
+                                for (auto& f : s.second)
+                                {
+                                    for (auto& v : s2[tmp])
+                                    {
+                                        vector<string> tp = f;
+                                        tp.insert(tp.end(), v.rbegin(), v.rend());
+                                        res.emplace_back(tp);
+                                    }
+                                }
+                            }
+                            else
+                            {
+                                for (auto& f : s.second)
+                                {
+                                    for (auto& v : s2[tmp])
+                                    {
+                                        vector<string> tp = v;
+                                        tp.insert(tp.end(), f.rbegin(), f.rend());
+                                        res.emplace_back(tp);
+                                    }
+                                }
+                            }
+                        }
+                        for (auto& p : s.second) 
+                        {
+                            vector<string> tp = p;
+                            tp.push_back(tmp);
+                            stack[tmp].emplace_back(tp);
+                        }
+                    }
+                }  
+            }   
+            s1 = stack.size() < s2.size() ? stack : s2;
+            s2 = stack.size() < s2.size() ? s2 : stack;
+            ++step;
+            if (!res.empty() and step > res[0].size()) return res;
+        }
+        return res;
+    }
+};

src/0126-Word-Ladder-II/0126.py

@@ -0,0 +1,35 @@
+from collections import defaultdict
+class Solution:
+    def findLadders(self, beginWord, endWord, wordList):
+        wordDict, res = set(wordList), []
+        if endWord not in wordDict:
+            return res
+
+        s1, s2, step = defaultdict(list), defaultdict(list), 2
+        s1[beginWord].append([beginWord])
+        s2[endWord].append([endWord])
+        while s1:
+            stack = defaultdict(list)
+            wordDict -= s1.keys()
+
+            for w, paths in s1.items():
+                for i in range(len(w)):
+                    for j in string.ascii_lowercase:
+                        tmp = w[:i] + j + w[i+1:]
+                        if tmp not in wordDict:
+                            continue
+                        if tmp in s2:
+                            if paths[0][0] == beginWord:
+                                res += [f + b[::-1] for f in paths for b in s2[tmp]]
+                            else:
+                                res += [b + f[::-1] for f in paths for b in s2[tmp]]
+                        stack[tmp] += [p + [tmp] for p in paths]
+            
+            if len(stack) < len(s2):
+                s1 = stack
+            else:
+                s1, s2 = s2, stack
+            step += 1
+            if res and step > len(res[0]):
+                return res
+        return res