Where can we see that  this algorithm use the divide and conquer techniques?




2010/11/7 Pratik Bhadkoliya <pkbhadkol...@gmail.com>

> A Linear-time Majority Vote Algorithm
>
> Problem: How to decide, in one pass which element of a sequence is in the
> majority, provided there is such an element.
>
> As we sweep through the sequence, we maintain a pair consisting of a
> current candidate and a counter. Initially, the current candidate is unknown
> and the counter is 0. When we move the pointer forward over an element e:
>
>    - If the counter is 0, we set the current candidate to e and we set the
>    counter to 1.
>    - If the counter is not 0, we increment or decrement the counter
>    according to whether e is the current candidate. When we are done, the
>    current candidate is the majority element, if there is a majority.
>
> If you must confirm that the chosen element is indeed the majority element,
> you must take one more linear pass through the data to do it.
>
> if Counter is greater than 0 at the end then we get the majority element in
> candidate field.
>
> Now, just count the number of times it occurred in the list using one more
> traversal and if now this count is greater than n/2 then return true or
> false otherwise.
>
> So, total pass = 2n -> order is O(n)
> On Sun, Nov 7, 2010 at 11:15 AM, Ashim Kapoor <ashimkap...@gmail.com>wrote:
>
>> Is'nt this solvable by the majority vote algorithm already discussed in
>> this list?
>>
>> Ashim.
>>
>>
>> On Sun, Nov 7, 2010 at 3:42 AM, lichenga2404 <lichenga2...@gmail.com>wrote:
>>
>>> There are many secret groups in College A.Every student at college A
>>> is a member or these secret group, though membership in one excludes a
>>> student from joining any other group. You wish to determine if any one
>>> of these groups contains more than half of the student population. To
>>> achieve this , you will introduce 2 students to each other: if they
>>> are members of different group , they will smile. If different group ,
>>> they will nod. How to determine if any one group has more than half of
>>> the student population as members in O(n) introductions . And justify
>>> the answer.
>>>
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licheng

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