How do a find the maximum non-repeating number in an integer array?

Question

Suppose I have an unsorted integer array {3, -1, 4, 5, -3, 2, 5}, and I want to find the maximum non-repeating number (4 in this case) (5 being invalid as it is repeated). How c

Answer 1

1. Sort the array in descending order.
2. Begin from top element and store it a variable, say max.
3. Check next element with max, if they are the same, repeat until you find the next max, otherwise, you found the max non-repeated number.

Time complexity: O(nlogn)

c++ implementation, based on my Sort (C++):

#include 
#include 
#include 
#include 
#include 

using namespace std;

void printVector(vector& v)
{
    for(vector::iterator it = v.begin() ; it != v.end() ; it++)
        cout << *it << ' ';
    cout << endl;
}

bool compar(const int& a, const int& b)
{
    return (a > b) ? true : false;
}


int main()
{
    vector v = {3, -1, 4, 5, -3, 2, 5};
    cout << "Before sorting : " << endl;
    printVector(v);

    sort(v.begin(), v.end(), compar);

    cout << endl << "After sorting : " << endl;
    printVector(v);


    int max_non_repeat = numeric_limits::min();
    for(unsigned int i = 0; i < v.size(); ++i)
    {
        if(max_non_repeat == v[i])
            max_non_repeat = numeric_limits::min();
        else if(v[i] > max_non_repeat)
            max_non_repeat = v[i];
    }

    cout << "Max non-repeated element: " << max_non_repeat << endl;

    return 0;
}

Output:

C02QT2UBFVH6-lm:~ gsamaras$ g++ -Wall -std=c++0x  main.cpp 
C02QT2UBFVH6-lm:~ gsamaras$ ./a.out 
Before sorting : 
3 -1 4 5 -3 2 5 

After sorting : 
5 5 4 3 2 -1 -3 
Max non-repeated element: 4

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For maximum pleasure, do base your (a different) approach on How to find max. and min. in array using minimum comparisons? and modify it accordingly.