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segregate 0 on left and 1 on right in 0(n)

(6 posts)

1. 

   kapil
   guest
   Posted 1 year ago #
   
   

   an array of 0 and 1 in random order, segregate 0 on left and 1 on right in 0(n)

2. 

   Naveen
   guest
   Posted 1 year ago #
   
   

   loop through the array and find out how many 0's and 1's are present. Let's say number of 0's are M and number of 1's are N. Modify the first M elements of the array to 0 and the rest to 1.

3. 

   kapil
   guest
   Posted 1 year ago #
   
   

   @Naveen
   I suggested the same approac in my interview, but interviewer asked me to do it in single pass.

   I missed to mention it in my original question.

4. 

   Gautham
   Member
   Posted 1 year ago #
   
   

   You can maintain a queue containing position of 1's. If you encounter a 0 and the queue is non empty, pop a position from the queue, modify its value to 0, modify the current position value as 1 and push it to the queue.

5. 

   Sandeep
   Moderator
   Posted 1 year ago #
   
   

   Maintain two indexes. Initialize first index left as 0 and second index right as n-1.

   Keep on incrementing left index while there are 0s at it
   Keep on decrementing right index while there are 1s at it
   Now if left < right then exchange arr[left] and arr[right]

   void segregate0and1(int arr[], int size)
   {
     /* Initialize left and right indexes */
     int left = 0, right = size-1;     
   
     while(left < right)
     {
        /* Increment left index while we see 0 at left */
        while(arr[left] == 0 && left < right)
           left++;
   
        /* Decrement right index while we see 1 at right */
        while(arr[right] == 1 && left < right)
           right--;
   
       /* If left is smaller than right then there is a 1 at left
         and a 0 at right.  Exchange arr[left] and arr[right]*/
        if(left < right)
        {
          arr[left] = 0;
          arr[right] = 1;
          left++;
          right--;
        }
     }
   }     
   
   int main()
   {
     int arr[] = {0, 1, 0, 1, 1, 1};
     int arr_size = 6, i = 0;
   
     segregate0and1(arr, arr_size);
   
     printf("array after segregation ");
     for(i = 0; i < 6; i++)
       printf("%d ", arr[i]);
   
     getchar();
     return 0;
   }
   

6. 

   GeeksforGeeks
   Key Master
   Posted 1 year ago #
   
   

   @kapil and @Naveen: This has been published.

   Please see http://geeksforgeeks.org/?p=5234

   Thanks for your contribution to the portal. Keep it up!!

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