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C Program To Segregate 0s and 1s In An Array using Swapping Method

Write a C program to segregate 0’s to the left and 1’s to the right of an array using Swapping method.

Related Read:
C Program To Segregate 0s and 1s In An Array using Counting Method

Example: Expected Input/Output

Enter 10 elements(0 or 1)
1
0
1
0
1
0
1
0
1
0

Array after sorting 0’s to left and 1’s to right
0
0
0
0
0
1
1
1
1
1

Visual Representation

Segregate 0s and 1s In An Array

Video Tutorial: C Program To Segregate 0’s and 1’s In An Array using Swapping Method


[youtube https://www.youtube.com/watch?v=AqJM2WtkeEU]

YouTube Link: https://www.youtube.com/watch?v=AqJM2WtkeEU [Watch the Video In Full Screen.]

Source Code: C Program To Segregate 0’s and 1’s In An Array using Swapping Method

#include<stdio.h>

#define N 5

int main()
{
    int a[N], i, left = 0, right = N - 1;

    printf("Enter %d elements(0 or 1)\n", N);
    for(i = 0; i < N; i++)
    {
        scanf("%d", &a[i]);

        if(a[i] != 0 && a[i] != 1)
        {
            printf("Please enter only 0 and 1 as input\n");
            i--;
        }
    }

    while(left < right)
    {
        while(a[left]   == 0)
            left++;

        while(a[right] == 1)
            right--;

        if(left < right)
        {
            a[left++] = 0;
            a[right--] = 1;
        }
    }

    printf("\nArray after sorting 0's to left and 1's to right\n");
    for(i = 0; i < N; i++)
        printf("%d\n", a[i]);

    printf("\n");

    return 0;
}

Output 1:
Enter 5 elements(0 or 1)
1
0
0
1
0

Array after sorting 0’s to left and 1’s to right
0
0
0
1
1

Output 2:
Enter 5 elements(0 or 1)
2
Please enter only 0’s and 1’s as input
10
Please enter only 0’s and 1’s as input
1
0
2
Please enter only 0’s and 1’s as input
1
1
0

Array after segregating o’s to left and 1’s to right
0
0
1
1
1

Logic To Segregate 0’s and 1’s In An Array using Swapping Method

We ask the user to input N integer numbers and store it inside a[N]. We assign 0(the first index of any array) to variable left and N – 1(the last index of any array) to variable right.

The outer while loop executes until left < right. Inside we write another while loop to check from left, if a[left] is 0. If its already 0, then its already in sorted order, so we don’t swap it. We simply increment the value of left by one position. Control exits this first inner while loop when a[left] is not equal to 0.

Similarly, we check if a[right] is 1. If its 1, we decrement the value of right by 1. When a[right] is not equal to 1, the control exits.

Now variable “left” will have the index position from left where there is number 1. And variable “right” will have the index position from right where there is number 0. Now we need to swap it.

We check if value of left is still less than the value of right. If true, we store 0 at a[left] and 1 at a[right].

Explanation With Example

If a[5] = {0, 1, 1, 0, 1};

lefta[left]righta[right]Swap
0041NO
1130YES
2121NO

a[5] after sorting 0’s to left and 1’s to right:
a[5] = {0, 0, 1, 1, 1};

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For full C programming language free video tutorial list visit:C Programming: Beginner To Advance To Expert

C Program To Segregate 0s and 1s In An Array using Counting Method

Write a C program to segregate 0’s to the left and 1’s to the right of an array using counting method.

Related Read:
C Program To Segregate 0s and 1s In An Array using Swapping Method

Example: Expected Input/Output

Enter 10 elements(0 or 1)
1
0
0
1
1
1
1
0
0
1

Array after segregating o’s to left and 1’s to right
0
0
0
0
1
1
1
1
1
1

Visual Representation

Segregate 0s and 1s In An Array

Video Tutorial: C Program To Segregate 0’s and 1’s In An Array using Counting Method


[youtube https://www.youtube.com/watch?v=gHW6WI-5724]

YouTube Link: https://www.youtube.com/watch?v=gHW6WI-5724 [Watch the Video In Full Screen.]

Source Code: C Program To Segregate 0’s and 1’s In An Array using Counting Method

#include<stdio.h>

#define N 5

int main()
{
    int a[N], i, count = 0;

    printf("Enter %d elements(0 or 1)\n", N);
    for(i = 0; i < N; i++)
    {
        scanf("%d", &a[i]);
        if(a[i] != 0 && a[i] != 1)
        {
            printf("Please enter only 0's and 1's as input\n");
            i--;
        }
        else if(a[i] == 0)
            count++;
    }

    for(i = 0; i < N; i++)
    {
        if(i < count)
            a[i] = 0;
        else
            a[i] = 1;
    }

    printf("\nArray after segregating o's to left and 1's to right\n");
    for(i = 0; i < N; i++)
        printf("%d\n", a[i]);

    printf("\n");

    return 0;
}

Output 1:
Enter 5 elements(0 or 1)
0
1
1
0
0

Array after segregating o’s to left and 1’s to right
0
0
0
1
1

Output 2:
Enter 5 elements(0 or 1)
2
Please enter only 0’s and 1’s as input
10
Please enter only 0’s and 1’s as input
1
0
2
Please enter only 0’s and 1’s as input
1
1
0

Array after segregating o’s to left and 1’s to right
0
0
1
1
1

Logic To Segregate 0’s and 1’s In An Array using Counting Method

We ask the user to input N integer numbers and store it inside a[N]. Next we iterate through each element of the array and if the user input is 0, then we increment the value of variable count by 1. After completing the iterations, variable count will have the number of 0’s input by the user.

Modifying the Array
Since user is allowed to either enter 0 or 1. So if we know the number of 0’s input by the user, we can easily calculate the number of 1’s in the array, using the formula:

N – count_0 = count_1
where, N is array size.

Now that we know the exact number of 0’s and 1’s input by the user, we re-enter the 0’s and 1’s as needed by the problem statement. That is, we arrange all the 0’s to left and 1’s to the right.

Number of 0’s plus the number of 1’s should be equal to the array size.
count_0 + count_1 = N;

Explanation With Example

If a[5] = {0, 1, 1, 0, 1};

ia[i]count
001
11
21
302
41

count = 2;
That is, the number of 0’s in user input array is 2. So the number of 1’s is:
array_size – count
5 – 2 = 3
So there are three 1’s and two 0’s.

    for(i = 0; i < N; i++)
    {
        if(i < count)
            a[i] = 0;
        else
            a[i] = 1;
    }

Once we have this exact data. We can arrange Two 0’s from left of array, i.e., a[0] and a[1]. And three 1’s from a[2], a[3] and a[4].

This is how we segregate 0’s to left and 1’s to the right of an array, using counting method.

For list of all c programming interviews / viva question and answers visit: C Programming Interview / Viva Q&A List

For full C programming language free video tutorial list visit:C Programming: Beginner To Advance To Expert