2019-07-25

Author: JiayangWu

0207.课程表/0207-课程表.py

@@ -0,0 +1,35 @@
+class Solution(object):
+    def canFinish(self, numCourses, prerequisites):
+        """
+        :type numCourses: int
+        :type prerequisites: List[List[int]]
+        :rtype: bool
+        """
+        from collections import deque
+        if not prerequisites: #没有前置课的要求
+            return True
+        
+        indegree = [0 for _ in range(numCourses)]
+        adj = [set() for _ in range(numCourses)]
+        
+        for end, start in prerequisites:
+            indegree[end] += 1
+            adj[start].add(end)
+        
+        queue = deque()
+        for i, x in enumerate(indegree):
+            if not x: #入度为0的结点入队
+                queue.append(i)
+        
+        cnt = 0
+        while queue:
+            cur = queue.popleft()
+            cnt += 1 #当前的cur满足条件
+            
+            for neighbor in adj[cur]:
+                indegree[neighbor] -= 1
+                if not indegree[neighbor]:
+                    queue.append(neighbor)
+    
+        return cnt == numCourses
+                    

0208.实现Trie(前缀树)/0208-实现Trie(前缀树).py

@@ -5,7 +5,6 @@ def __init__(self):
         Initialize your data structure here.
         """
         self.root = {}
-        
 
     def insert(self, word):
         """
@@ -16,10 +15,8 @@ def insert(self, word):
         node = self.root
         for char in word:
             node = node.setdefault(char, {})
-        
-        node["end"] = True
 
-        
+        node["end"] = True
 
     def search(self, word):
         """
@@ -32,9 +29,7 @@ def search(self, word):
             if char not in node:
                 return False
             node = node[char]
-            
         return "end" in node
-        
 
     def startsWith(self, prefix):
         """
@@ -47,7 +42,6 @@ def startsWith(self, prefix):
             if char not in node:
                 return False
             node = node[char]
-        
         return True
 
 

0209.长度最小的子数组/0209-长度最小的子数组.py

@@ -7,22 +7,20 @@ def minSubArrayLen(self, s, nums):
         """
         if not nums:
             return 0
-        res = len(nums) + 1
-        lo, hi = 0, -1
-        subsum = 0
-        while(lo < len(nums)):
-           
-            if subsum < s and hi + 1 < len(nums):
-                hi += 1
-                subsum += nums[hi]                
-            else:                
-                subsum -= nums[lo]
-                lo += 1
-                
-            if subsum >= s:
-                res = min(res, hi - lo + 1)
-                
-        return res if res != len(nums) + 1 else 0
-            
 
+        left, right = 0, 0
+        interval_sum = nums[0]
+        res = 1 << 31
+        while right < len(nums) and left <= right:
+            # print nums[left:right + 1], interval_sum, left, right
+            if interval_sum < s:
+                right += 1 #需要更多的数，向右拓展
+                if right < len(nums):
+                    interval_sum += nums[right]
+            else:
+                res = min(res, right - left + 1)                
+                interval_sum -= nums[left]
+                left += 1 #满足条件，试着缩小区间
+        # res = min(res, right - left + 1)
+        return res if res != 1 <<31 else 0
 

0210.课程表II/0210-课程表II.py

@@ -0,0 +1,35 @@
+class Solution(object):
+    def findOrder(self, numCourses, prerequisites):
+        """
+        :type numCourses: int
+        :type prerequisites: List[List[int]]
+        :rtype: List[int]
+        """
+        if not prerequisites:
+            return [i for i in range(numCourses)]
+        
+        indegree = [0 for _ in range(numCourses)]
+        adj = [set() for _ in range(numCourses)]
+        
+        for end, start in prerequisites:
+            indegree[end] += 1
+            adj[start].add(end)
+            
+        from collections import deque
+        queue = deque()
+        
+        for i, x in enumerate(indegree):
+            if not x:
+                queue.append(i)
+                
+        res = []
+        while queue:
+            cur = queue.popleft()
+            res.append(cur)
+            
+            for neighbor in adj[cur]:
+                indegree[neighbor] -= 1
+                if indegree[neighbor] == 0:
+                    queue.append(neighbor)
+                    
+        return res if len(res) == numCourses else []

0211.添加与搜索单词-数据结构设计/0211-添加与搜索单词-数据结构设计.py

@@ -0,0 +1,46 @@
+class WordDictionary(object):
+
+    def __init__(self):
+        """
+        Initialize your data structure here.
+        """
+        self.roots = {}
+
+    def addWord(self, word):
+        """
+        Adds a word into the data structure.
+        :type word: str
+        :rtype: None
+        """
+        print word
+        node = self.roots
+        for char in word:
+            node = node.setdefault(char, {})
+        node["end"] = True
+
+    def search(self, word):
+        """
+        Returns if the word is in the data structure. A word could contain the dot character '.' to represent any one letter.
+        :type word: str
+        :rtype: bool
+        """
+        self.res = False
+        self.searchHelper(self.roots, word)
+        return self.res
+
+    def searchHelper(self, dic, word):
+        if not word:
+            self.res |= "end" in dic
+            return
+        node = dic
+        i, char = 0, word[0]
+        if char == ".":#È«Æ¥Åä
+            for x in "abcedfghijklmnopqrstuvwxyz":
+                if x in node:
+                    self.searchHelper(node[x], word[1:])
+        elif char in node:
+            self.searchHelper(node[char], word[1:])
+# Your WordDictionary object will be instantiated and called as such:
+# obj = WordDictionary()
+# obj.addWord(word)
+# param_2 = obj.search(word)

0212.单词搜索II/0212-单词搜索II.py

@@ -0,0 +1,84 @@
+class Trie(object):
+    def __init__(self):
+        """
+        Initialize your data structure here.
+        """
+        self.root = {}
+
+    def insert(self, word):
+        """
+        Inserts a word into the trie.
+        :type word: str
+        :rtype: None
+        """
+        node = self.root
+        for char in word:
+            node = node.setdefault(char, {})
+            
+        node["end"] = True
+
+    def search(self, word):
+        """
+        Returns if the word is in the trie.
+        :type word: str
+        :rtype: bool
+        """
+        node = self.root
+        for char in word:
+            if char not in node:
+                return False
+            node = node[char]
+        return "end" in node
+
+    def startsWith(self, prefix):
+        """
+        Returns if there is any word in the trie that starts with the given prefix.
+        :type prefix: str
+        :rtype: bool
+        """
+        node = self.root
+        for char in prefix:
+            if char not in node:
+                return False
+            node = node[char]
+        return True
+
+class Solution(object):
+    def findWords(self, board, words):
+        """
+        :type board: List[List[str]]
+        :type words: List[str]
+        :rtype: List[str]
+        """
+        if not board or not board[0]:
+            return []
+        m, n = len(board), len(board[0])
+        dx = [1, -1, 0, 0]
+        dy = [0, 0, 1, -1]
+        tree = Trie()
+        for word in words:
+            tree.insert(word)
+        words = set(words)
+        res = set()
+        def dfs(x0, y0, node, tmpword):
+            visited.add((x0, y0))
+            # print tmpword, x0, y0
+            for k in range(4):
+                x = x0 + dx[k]
+                y = y0 + dy[k]
+                
+                if 0 <= x < m and 0 <= y < n and board[x][y] in node and (x, y) not in visited:
+                    visited.add((x, y))
+                    dfs(x, y, node[board[x][y]], tmpword + board[x][y])
+                    visited.remove((x,y))
+                    
+            if tmpword in words:
+                res.add(tmpword)
+                    
+        for i in range(m):
+            for j in range(n):
+                if board[i][j] in tree.root:
+                    visited = set((i,j))
+                    dfs(i, j, tree.root[board[i][j]], board[i][j])
+        return list(res)
+