Question

I have any array with value 0,0,0,0,0,0,0,0,1,1,1
Now my required output should be like each zero will be in odd index and 1 will be in even and if 0 left after that it should be copied after 1 and viceversa.
Means the output will be 0,1,0,1,0,1,0,0,0,0,0….
But the above operation must be done in a single pass of array

• So I created an array with same size ,
• then I started traversing the main array and one’s 0 is encoutered I put a counter to set the value in odd index and viceversa
• In the end when the index crossed the length of new array created , I started adding the 0 into the new cell in even mode from backward.

What can be the other better solution.

Answer 1

You don’t need an extra array for this. You can do it in-place. Just keep two pointers, one which stops after every odd step and one which finds the 1s. When the second pointer encounters a 1 just swap it with the first pointer, increment the first pointer. Do this for the length of the array.