36 lines
716 B
Ruby
36 lines
716 B
Ruby
|
# Find majority element(if exists) in a given array.
|
||
|
|
# A majority element in an array A[] of size n is an element that appears more than n/2 times
|
||
|
|
#Time-complexity: O(n), Auxiliary-space:O(1)
|
||
|
|
|
||
|
|
|
||
|
|
#Moore's Voting algorithm
|
||
|
|
def majority_element(a)
|
||
|
|
len=a.length
|
||
|
|
maj_index=0
|
||
|
|
count=1
|
||
|
|
for i in 1...len
|
||
|
|
if a[i]==a[maj_index]
|
||
|
|
count+=1
|
||
|
|
else
|
||
|
|
count-=1
|
||
|
|
end
|
||
|
|
if count==0
|
||
|
|
a[maj_index]=a[i]
|
||
|
|
count=1
|
||
|
|
end
|
||
|
|
end
|
||
|
|
candidate=a[maj_index]
|
||
|
|
count=0
|
||
|
|
for i in 0...len
|
||
|
|
if a[i]==candidate
|
||
|
|
count+=1
|
||
|
|
end
|
||
|
|
end
|
||
|
|
|
||
|
|
if count > (len/2)
|
||
|
|
return candidate
|
||
|
|
else
|
||
|
|
return -1
|
||
|
|
end
|
||
|
|
end
|
||
|
|
majority_element([2, 2, 3, 5, 2, 3])
|