Majority Element

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  1. Boyer-Moore Majority Vote

Time: O(n) Space: O(1)

Step 1. Iterate through the array:

if counter = 0 { current candidate = x; counter = 1}

else {

if current x = candidate {counter ++}

else {counter –}


Step 2. Determine if the remaining element is a valid majority element

With Step 1 candidate, iterate through array to check the occurrences.

Screen Shot 2015-10-05 at 7.04.56 PM

2. HashTable 

Time: O(n) Space: O(n)

Hash table stores the occurrence frequency of each element.

Pick out the one with frequency > [n/2]

Screen Shot 2015-10-05 at 7.21.48 PM


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