Sorting/grouping odd and even numbers in odd and even segregated list

Question

I have a unsorted list of number with even and odd. I need to segregate odd and even numbers in sorted order.

For example:

List = [5,6,4,7,11,14,12,1,3]

Expected output :

[4,6,12,14,1,3,5,7,11]

My program to segregate the odd and even numbers.

L = [5,6,4,7,11,14,12,1,3]
def segregateEvenOdd(L):
    left,right = 0,len(L)-1
    while left < right:
        while (L[left]%2==0 and left < right):
            left += 1
        while (L[right]%2 == 1 and left < right):
            right -= 1
        if (left < right):
            L[left],L[right] = L[right],L[left]
            left += 1
            right = right-1

print segregateEvenOdd(L)

output : [12, 6, 4, 14, 11, 7, 5, 1, 3]

I am trying to sort the list using insertion sort, couldn't get right output. Any way to sort this easily

create two sorted lists using `filter`, `lambda` and `sorted` and then concatenate them with `+`. — Ma0, Apr 16 '18 at 07:48

fferri · Accepted Answer · 2022-01-17T11:21:37.623

8

Using a key function for list.sort / sorted:

>>> list(sorted(lst, key=lambda x: [x % 2, x]))
[4, 6, 12, 14, 1, 3, 5, 7, 11]

maps even numbers n to the value [0, n], and odd numbers n to the value [1, n], so that even numbers come first according to natural ordering of list items, i.e. [0, ...] comes before [1, ...].

edited Jan 17 '22 at 11:21

answered Apr 16 '18 at 07:55

fferri

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Shijith · Answer 2 · 2021-09-08T08:03:02.987

Adding to @fferi 's answer.
if you want even numbers followed by odd numbers , each in ascending order, do:

>>> lst=range(10)
>>> sorted(lst, key = lambda x:(x%2, x))
[0, 2, 4, 6, 8, 1, 3, 5, 7, 9]

odd numbers followed by even numbers , each in ascending order

>>> sorted(lst, key = lambda x:(not x%2, x))
[1, 3, 5, 7, 9, 0, 2, 4, 6, 8]

even numbers followed by odd numbers , each in descending order

>>> sorted(lst, key = lambda x:(not x%2, x), reverse=True)
[8, 6, 4, 2, 0, 9, 7, 5, 3, 1]

odd numbers followed by even numbers , each in descending order

>>> sorted(lst, key = lambda x:(x%2, x), reverse=True)
[9, 7, 5, 3, 1, 8, 6, 4, 2, 0]

Nice and details on each Use Cases. Challenge: sort *odds* on ascending, but *evens* on descending ordering? — Daniel Hao, Oct 02 '22 at 12:45

Achu · Answer 3 · 2020-04-20T17:08:18.400

3

Short_list =[5,7,3,2,8,1,0,10,9,4,6]
def sort_list(my_list):
  even_list = []
  odd_list = []
  for i in my_list:
      if i % 2 == 0:
          even_list.append(i)
      else:
          odd_list.append(i)
  even_list.sort(),odd_list.sort()
  even_list.extend(odd_list)
  return even_list

print(sort_list(Short_list))

[0, 2, 4, 6, 8, 10, 1, 3, 5, 7, 9]

edited Apr 20 '20 at 17:08

answered Apr 20 '20 at 17:02

Achu

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score 2 · Answer 4 · answered Apr 16 '18 at 07:53

2

Simply use list comprehension basics

>>> arr = [5,6,4,7,11,14,12,1,3]
>>> evens = sorted([e for e in arr if e % 2 ==0])
>>> odds = sorted([e for e in arr if e % 2 !=0])
>>> print(evens + odds)
[4, 6, 12, 14, 1, 3, 5, 7, 11]

answered Apr 16 '18 at 07:53

ProgSnob

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Thierry Lathuille · Answer 5 · 2018-04-16T08:07:38.393

2

We can first sort on n%2 (n modulo 2), which will be 0 for odd numbers and 1 for even ones, then on the number itself:

L = [5,6,4,7,11,14,12,1,3]
out = sorted(L, key = lambda n:(n%2, n))

print(out)
# [4, 6, 12, 14, 1, 3, 5, 7, 11]

The tuples we use as a key are sorted according to their first item first, then to their second.

And it will also work for negative numbers...

edited Apr 16 '18 at 08:07

answered Apr 16 '18 at 08:02

Thierry Lathuille

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Austin · Answer 6 · 2018-04-16T08:02:08.490

1

Make a list of evens and list of odds and then combine:

lst = [5,6,4,7,11,14,12,1,3]
even = sorted([i for i in lst if i%2 == 0])
odd = sorted([i for i in lst if i%2])
print(even + odd)

Or using filter, lambda:

lst = [5,6,4,7,11,14,12,1,3]
lst.sort()

even = list(filter(lambda x: not x%2, lst))
odd = list(filter(lambda x: x%2, lst))

print(even + odd)

edited Apr 16 '18 at 08:02

answered Apr 16 '18 at 07:53

Austin

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Giuseppe Angora · Answer 7 · 2018-05-25T08:48:01.850

1

A simple solution:

import numpy as np
l = [5,6,4,7,11,14,12,1,3]
l_sort = np.sort(l) #sorting elements of the list
evens = list(filter(lambda x: x%2==0, l_sort)) #extract even elements 
odds = list(filter(lambda x: x%2!=0, l_sort)) #extract odd elements
out = evens + odds

edited May 25 '18 at 08:48

answered Apr 16 '18 at 07:55

Giuseppe Angora

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jpp · Answer 8 · 2018-04-16T08:25:34.467

1

If you are happy to use a 3rd party library, you can use Boolean indexing with numpy.

numpy.lexsort sorts in reverse fashion, i.e. it considers A % 2 before A:

import numpy as  np

A = np.array([4,6,12,14,1,3,5,7,11])

res = A[np.lexsort((A, A % 2))]

# [ 4  6 12 14  1  3  5  7 11]

Related: Why NumPy instead of Python lists?

edited Apr 16 '18 at 08:25

answered Apr 16 '18 at 08:10

jpp

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score 1 · Answer 9 · answered Apr 16 '18 at 09:33

1

i suggest this if you want to avoid using external libraries:

def even_odd_sort(list):
evens=[]
odds=[]
for i in list:
    if(i%2==0):
        evens.append(i)
    else:
        odds.append(i)
evens.sort()
odds.sort()
return evens+odds

answered Apr 16 '18 at 09:33

M.H Mighani

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Michael Chinchay · Answer 10 · 2020-03-07T04:07:54.517

the process involve to split the values into even and odd numbers in a separate temporary list, then sort them numerically in a ascending order and finally putting together all in one list. The pictures below shows two projects on C#, one with all the process while the second one is more practical but the process works for your project.

Steps:

Split the original list in two, one for even and another for odds.
With Both List, Sort them in ascending order.
Now Merge both list in one list.

This is all the C# Code, I hope this helps, Better Late than Never:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            combodata1();
        }

        public void combodata1() {
            combo1.DataSource = new String[] {"5","10","15","20","25","30","35","40"};
        }

        private void button2_Click(object sender, EventArgs e)
        {
            generate();
        }

        List<String> li1 = new List<String>();
        List<String> li2 = new List<String>();
        List<String> li3 = new List<String>();
        List<String> li4 = new List<String>();
        List<String> li5 = new List<String>();

        public void generate() {

            li1.Clear();

            int r = Convert.ToInt32(combo1.SelectedValue)-1;

            Random ran = new Random();

            for(int i=0;i<=r;i++){

                int num1 = ran.Next(100);
                li1.Add(Convert.ToString(num1));

                                 }

            lista1.DataSource = null;
            lista1.DataSource = li1;

                               }

        private void button1_Click(object sender, EventArgs e)
        {
            String te1 = data1.Text;

            if (te1.Equals("") == false)
            {
                add();
            }

            else {
                MessageBox.Show("- You need to add integer numbers only, empty space or letters are not allowed.","Message");
            }
        }

        public void add() {
            String dato = data1.Text;
            li1.Add(dato);
            lista1.DataSource = null;
            lista1.DataSource = li1;
            data1.Text = "";
                              }

        private void button3_Click(object sender, EventArgs e)
        {          
            int n = lista1.Items.Count;

            if(n>0){
            split();
                   }

            else {
                MessageBox.Show("- Original List must present values.","Message");
                 }
        }

        public void split() {

            int n = lista1.Items.Count-1;

            for (int i = 0; i <= n;i++){

                double a = Convert.ToDouble(li1.ElementAt(i));
                double b = (a / 2);
                double c = b - Math.Floor(b);

                if (c == 0){
                    li2.Add(Convert.ToString(a));
                           }

                else {
                    li3.Add(Convert.ToString(a));
                     }

                                       }

            sort_evenly();

                              }

        public void sort_evenly() {

            int w = li2.Count;

            if (w > 0)
            {

                int n = li2.Count - 1;

                int a = Convert.ToInt32(li2.ElementAt(0));

                for (int i = 1; i <= n; i++)
                {

                    int b = Convert.ToInt32(li2.ElementAt(i));

                    if (a > b) { a = b * 1; }
                    if (a < b) { a = a * 1; }

                }

                li4.Add(Convert.ToString(a));
                li2.Remove(Convert.ToString(a));

                sort_evenly();

            }

            else {
                sort_oddly();
                 }
                                  }

        public void sort_oddly() {

            int w = li3.Count;

            if (w > 0)
            {

                int n = li3.Count - 1;

                int a = Convert.ToInt32(li3.ElementAt(0));

                for (int i = 1; i <= n; i++)
                {

                    int b = Convert.ToInt32(li3.ElementAt(i));

                    if (a < b) { a = a * 1; }
                    if (a > b) { a = b * 1; }

                }

                li5.Add(Convert.ToString(a));
                li3.Remove(Convert.ToString(a));

                sort_oddly();

            }

            else {
               sortedlist();
                 }
                                    }

        String even = "";
        String odd = "";
        String result = "";

        public void sortedlist() {

            even = "";
            odd = "";
            result = "";

            int n = li4.Count-1;
            int k = li5.Count-1;

            for(int i=0;i<=n;i++){
            String hyphen = "-";
            if(i==n){hyphen="";}
            even = even + Convert.ToString(li4.ElementAt(i)) + hyphen;
                                 }

            for(int i=0;i<=k;i++){
            String hyphen = "-";
            if(i==k){hyphen="";}
            odd = odd + Convert.ToString(li5.ElementAt(i)) + hyphen;
                                 }

            result = even + "-" + odd;

            res1.Text = result;

            li2.Clear();
            li3.Clear();
            li4.Clear();
            li5.Clear();

        }

        private void button4_Click(object sender, EventArgs e)
        {
            clear();
        }

        public void clear() {
            li2.Clear();
            li3.Clear();
            li4.Clear();
            li5.Clear();
            res1.Text = "";
                               }

        private void button5_Click(object sender, EventArgs e)
        {
            clearall();
        }

        public void clearall() {
            data1.Text = "";
            li1.Clear();
            li2.Clear();
            li3.Clear();
            li4.Clear();
            li5.Clear();
            lista1.DataSource = null;
            res1.Text = "";
                              }
    }
}

score 1 · Answer 11 · edited Apr 08 '21 at 08:55

1

In python :

data = [100, 1, 2, 3, 4, 5, 6, 65, 89, 7, 8, 9, 10]
print(sorted([e for e in data if e % 2 == 0]) + sorted([e for e in data if e % 2 != 0]))

edited Apr 08 '21 at 08:55

STA

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answered Apr 08 '21 at 04:26

praveen kedar

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Y Logs · Answer 12 · 2022-06-13T05:54:42.053

1

My approach (long):

 l=[4,1,2,3]

 # separate odd and even position elements
 ev=[]
 odd=[]
 for i in range(len(l)):
     if i%2==0:
         ev.append(l[i])
     else:
         odd.append(l[i])

 # sort them
 newev = sorted(ev)
 newodd= sorted(odd, reverse=True)

 # combine them
 comb=list(zip(newev, newodd))

 # append according to the order
 out=[]
 for i, v in enumerate(op):
     out.append(v[0])
     out.append(v[1])

 print(out)
 # [2,3,4,1]

edited Jun 13 '22 at 05:54

answered Jun 12 '22 at 18:49

Y Logs

64
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Your answer could be improved with additional supporting information. Please [edit] to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers [in the help center](/help/how-to-answer). – Community Jun 12 '22 at 19:32

Sorting/grouping odd and even numbers in odd and even segregated list

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