2019-09-04

Author: JiayangWu

0277.搜寻名人/0277-搜寻名人.py

@@ -0,0 +1,26 @@
+# The knows API is already defined for you.
+# @param a, person a
+# @param b, person b
+# @return a boolean, whether a knows b
+# def knows(a, b):
+
+class Solution(object):
+    def findCelebrity(self, n):
+        """
+        :type n: int
+        :rtype: int
+        """
+        celebrity = 0
+        for i in range(1, n):
+            if knows(celebrity, i):
+                #说明当前的这个celebrity肯定不是名人，因为他认识别的人
+                celebrity = i
+        # 到这里的 celebrity，必定不认识 [celebrity + 1, n - 1]的所有人
+        for i in range(celebrity):
+            if knows(celebrity, i): # 为了确保celebrity 不认识 [0, celebrity - 1]
+                return -1
+        
+        for i in range(n):
+            if not knows(i, celebrity): # 为了确保 每个人都认识 celebrity
+                return -1
+        return celebrity

0278.第一个错误的版本/0278-第一个错误的版本.py

@@ -1,22 +1,19 @@
-
 # The isBadVersion API is already defined for you.
 # @param version, an integer
 # @return a bool
 # def isBadVersion(version):
-import math
+
 class Solution(object):
     def firstBadVersion(self, n):
         """
         :type n: int
         :rtype: int
         """
-        start = 1
-        end = n
-        while(end-start>1):
-            mid = start + (end-start)/2
+        left, right = 1, n
+        while left < right:
+            mid = (left + right) // 2
             if isBadVersion(mid):
-                end = mid
+                right = mid
             else:
-                start = mid
-            print start, end
-        return start if isBadVersion(start) else end
+                left = mid + 1
+        return left

0279.完全平方数/0279-完全平方数.py

@@ -1,29 +1,19 @@
-from collections import deque
 class Solution(object):
     def numSquares(self, n):
         """
         :type n: int
         :rtype: int
         """
-        record = []
-        for i in range(1, int(n ** 0.5) + 1):
-            record.append(i * i)
-        # print record
+        from collections import deque
+        queue = deque([(0, 0)])
         visited = set()
-        q = deque()
-        q.append([0, 0])
-        while(q):
-            m, cnt = q.popleft()
-            
-            for num in record:
-                s = m + num
+        while queue:
+            cur, step = queue.popleft()
+            for i in range(1, int(n ** 0.5) + 1):
+                s = cur + i ** 2
                 if s == n:
-                    return cnt + 1
-                if s < n and s not in visited:
+                    return step + 1
+                if s not in visited:
                     visited.add(s)
-                    q.append([s, cnt + 1])
-        # return
-                    
-            
-        
-        
+                    queue.append((s, step + 1))
+