leetcode#169 Majority Element

Problem Definition:

Given an array of size n, find the majority element. The majority element is the element, the appears more than times ⌊ n/2 ⌋ .

Assume that the array was non-empty and the majority element always exist in the array.

Solution 1: Use a dictionary to save the count, simple rough

1 def majorityelement (self,nums): 2     d={}3for in       nums:4        d.setdefault (i,0)  5         d[i]+=16         if d[i]>len (nums)/2:7             return I

Solution 2:1) Sort, 2) the value of the middle to the right position is the desired one; 3) Fastest O (nlogn)

Chestnuts: [4, 4,4,4] [1,1,1,1, 2,3]

1 def majorityelement (nums): 2         return Sorted (nums) [Len (Nums)/2]

Solution 3: Vote, same as the previous element cast 1, different cast -1,o (n)

1 defmajorityelement (self,nums):2major,count,n=0,0,len (nums)3      forIinchNums:4         ifcount==0:5Major=I6Count=17         Else:8count+= (1ifI==majorElse-1)9     returnMajor

Solution 4: Constantly randomly take a number, count, see luck.

Solution 5: Bitwise operation. (not known as the fur, when the array element is negative, major will become a long type, the whole does not work!!!!!!)

1 defmajorityelement (self,nums):2major,mask,n=0,1, Len (nums)3M=324      whileM>0:5Bc=06          forIinchNums:7             ifi&Mask:8Bc+=19             ifBc>n/2:Tenmajor|=Mask One                  Break AMask<<=1 -M-=1 -     returnMajor

leetcode#169 Majority Element