Please help me in solving

#1
#2

Please explain your code add some comments.

#3

I have added the comments

#4 
// as the couont increase to k we increase the j
      while (arr[j] != 1) {
        j++;//j increasing
      }
      countZero--;// decreasing the count
      j++;

You are increasing j till you dont find a 1 means you are iterating over zeroes. But only decreasing the count of countZero by 1 . Why ? I am unable to understand this part.
Did you mean to increase j till you find a zero. So the while loop must be the following.

      while (arr[j] != 0) {
        j++;    // j increasing till we dont find a zero.
      }
      countZero--;    // decreasing the count as we are removing 1 zero as countZero > k.
      j++;    // finally taking j to point after that 0.