Unique sort order of array c++

Question

How would I sort an array of integers (0,1,2,3,4,5) in a monge shuffle type order (greatest odd to least odd, then least even to greatest even) like (5,3,1,0,2,4). Im having trouble trying to solve this problem.

Ive tried so far:

void mongeShuffle(int A[], int B[], int size)
{
    int i = 0; // i is the index of the arr
    while(i < size)
    {
        if(A[i] % 2 == 1)
        {
            B[i] = A[i];
            i++;
        }
        else
        {
            B[i] = A[i -1];
            i++;
        }
    }
}

no were only allowed to use primitive functions

kxf951
– kxf951

2012-10-20 22:33:45 +00:00
Commented Oct 20, 2012 at 22:33 — kxf951
– kxf951, Commented Oct 20, 2012 at 22:33

Vikas · Accepted Answer · 2012-10-20 07:48:22Z

4

In c++ you can use algorithm header to use sort function and supply your custom comparator. Something like this:

#include <algorithm>
#include <iostream>

bool my_comp (int a, int b)
{
    if( a%2 == 1 && b%2 == 1)
    {  
        // Both odd
        return a > b;
    }
    else if( a%2 == 0 && b%2 == 0)
    {  
        // Both even
        return a < b;
    }
    else return a%2 == 1;
}

int main()
{
    int A[] = {0,1,2,3,4,5};
    std::sort(A, A + 6, my_comp);

    for(int i: A)
    {  
        std::cout << i << std::endl;
    }
}

edited Oct 20, 2012 at 7:48

answered Oct 20, 2012 at 7:32

Vikas

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5 Comments

PiotrNycz Over a year ago

There is 6 elements in the array - not 5. The last else should be else return a%2 == 1...

SwiftMango Over a year ago

4 test cases: both odd, both even, a is odd b is even, and a is even b is odd

Vikas Over a year ago

@texasbruce, the 3rd and 4th test cases both are covered by return a%2 == 1

Mankarse Over a year ago

The question was unclear, but this code does not perform a Monge Shuffle. A Monge Shuffle is based on the indices of the cards, not the values.

Vikas Over a year ago

@Mankarse, the question is ambiguous at this point. Based on OP's code, I thought he wants to sort similar to what Monge Shuffle does with indices. I'll remove it if OP clarifies or says this is not what he was looking for.

Mankarse · Accepted Answer · 2012-10-21 01:22:07Z

2

You need to shuffle based on the indices being even or odd, not the values.

#include <iostream>

void mongeShuffle(int A[], int B[], int size)
{
    for(int i = 0; i < size; ++i)
    {
        if(i % 2 == 0)
        {
            B[(size+i)/2] = A[i];
        }
        else
        {
            B[size/2 - i/2 - 1] = A[i];
        }
    }
}

edited Oct 21, 2012 at 1:22

answered Oct 20, 2012 at 7:06

Mankarse

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1 Comment

kxf951 Over a year ago

This really helped, but so far its working in opposite order such that: (0,1,2,3,4,5,6) would come out as (1,3,5,0,6,4,2) instead of (5,3,1,0,2,4,6)

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