Add files via upload

Author: assassint2017

Word Break/Word_Break.cpp

@@ -0,0 +1,91 @@
+// 简单的回溯 29 / 36 test cases passed. 超时了
+class Solution 
+{
+public:
+    bool wordBreak(string s, vector<string>& wordDict) 
+    {
+        if (s.length() == 0)
+            return true;
+        
+        for (int i = 0; i < s.length(); i++)
+        {
+            if (inWordDict(s.substr(0, i + 1), wordDict) && wordBreak(s.substr(i + 1), wordDict))
+                return true;
+        }
+        return false;
+    }
+private:
+    bool inWordDict(string &s, vector<string> &wordDict)
+    {
+        for (auto str: wordDict)
+        {
+            if (s == str)
+                return true;
+        }
+        return false;
+    }
+};
+
+// 思路二 同样使用回溯，区别在于对于思路一的代码进行加速
+// 29 / 36 test cases passed. 同样超时了
+class Solution 
+{
+public:
+    bool wordBreak(string s, vector<string>& wordDict) 
+    {
+        if (s.length() == 0)
+            return true;
+
+        for (auto word : wordDict)
+        {
+            if (s.substr(0, word.length()) == word)
+            {
+                if (wordBreak(s.substr(word.length()), wordDict))
+                    return true;
+            }
+        }
+        return false;   
+    }
+};
+
+
+// 思路三 区别与思路二就是加入了备忘录
+// Runtime: 8 ms, faster than 99.55% of C++ online submissions for Word Break.
+// Memory Usage: 9.9 MB, less than 87.92% of C++ online submissions for Word Break.
+
+class Solution 
+{
+public:
+    bool wordBreak(string s, vector<string>& wordDict) 
+    {
+        bool *visited = new bool[s.length() + 1]();
+        
+        bool res = helper(s, wordDict, visited);
+        
+        delete[] visited;
+        
+        return res;
+    }
+private:
+    bool helper(string s, vector<string>& wordDict, bool* visited)
+    {
+        if (visited[s.length()])
+            return false;
+        else
+        {
+            if (s.length() == 0)
+                return true;
+
+            for (auto word : wordDict)
+            {
+                if (s.substr(0, word.length()) == word)
+                {
+                    if (helper(s.substr(word.length()), wordDict, visited))
+                        return true;
+                }
+            }
+            visited[s.length()] = true;
+            return false;     
+        }
+    }
+};

Word Break/Word_Break.py

@@ -0,0 +1,21 @@
+# Runtime: 36 ms, faster than 98.71% of Python3 online submissions for Word Break.
+# Memory Usage: 12.7 MB, less than 18.75% of Python3 online submissions for Word Break.
+
+class Solution:
+    def wordBreak(self, s: 'str', wordDict: 'List[str]') -> 'bool':
+        visited = [False for i in range(len(s) + 1)]
+        
+        return self.helper(s, wordDict, visited)
+
+    def helper(self, s, wordDict, visited):
+        if visited[len(s)]:
+            return False
+        else:
+            if len(s) is 0:
+                return True
+            for word in wordDict:
+                if s[0:len(word)] == word:
+                    if self.helper(s[len(word):], wordDict, visited):
+                        return True
+            visited[len(s)] = True
+            return False