2020-06-21

Author: JiayangWu

1447.最简分数/1447-最简分数.py

@@ -1,11 +1,11 @@
 class Solution:
     def simplifiedFractions(self, n: int) -> List[str]:
         import math
-        res = set()
+        res = []
 
         for down in range(1, n + 1):
             for up in range(1, down):
                 if math.gcd(up, down) == 1:
-                    res.add(str(up) + "/" + str(down))
+                    res.append(str(up) + "/" + str(down))
 
-        return list(res)
+        return res

1460.通过翻转子数组使两个数组相等/1460-通过翻转子数组使两个数组相等.py

@@ -0,0 +1,9 @@
+class Solution(object):
+    def canBeEqual(self, target, arr):
+        """
+        :type target: List[int]
+        :type arr: List[int]
+        :rtype: bool
+        """
+        from collections import Counter
+        return Counter(target) == Counter(arr)

1461.检查一个字符串是否包含所有长度为K的二进制子串/1461-检查一个字符串是否包含所有长度为K的二进制子串.py

@@ -0,0 +1,15 @@
+class Solution(object):
+    def hasAllCodes(self, s, k):
+        """
+        :type s: str
+        :type k: int
+        :rtype: bool
+        """
+        numSet = set()
+        for i in range(len(s) - k + 1):
+            numSet.add(int(s[i:i + k], 2))
+        
+        for num in range(2 ** k):
+            if num not in numSet:
+                return False
+        return True

1462.课程安排IV/1462-课程安排IV.py

@@ -0,0 +1,37 @@
+class Solution(object):
+    def checkIfPrerequisite(self, n, prerequisites, queries):
+        """
+        :type n: int
+        :type prerequisites: List[List[int]]
+        :type queries: List[List[int]]
+        :rtype: List[bool]
+        """
+        from collections import defaultdict
+        from heapq import *
+        pre = defaultdict(set)
+        children = defaultdict(set)            
+        inDegree = defaultdict(int)
+            
+        for src, dec in prerequisites:
+            inDegree[dec] += 1
+            children[src].add(dec)
+
+        queue = []
+        for i in range(n):
+            if inDegree[i] == 0:
+                heappush(queue, i)
+                
+        while queue:
+            cur = heappop(queue)
+
+            for child in children[cur]:
+                pre[child] = pre[cur] | set([cur]) | pre[child]
+                
+                inDegree[child] -= 1
+                if inDegree[child] == 0:
+                    heappush(queue, child)
+
+        res = []
+        for src, dec in queries:
+            res.append(src in pre[dec])
+        return res