CareerCup

I'm not sure I understand your question. As it's phrases, you are getting the index input for an array of "4,7,44,47,74,77" Which doesn't seem a likely interview question. Can you clarify?

I did not understand the question .... why not 47 ??

public int findKth(int k)
{
	if(k<=0)
	{
		return -1;
	}
	if(k==1)
	{
		return 4;
	}
	if(k==2)
	{
		return 7;
	}
	int[] arr=new int[k+1];
	arr[1]=4;
	arr[2]=7;
	for(int i=3;i<arr.length;i++)
	{
		arr[i]=i%2!=0?(arr[(i>>2)]*10)+4:(arr[(i>>2)-1]*10)+7;
	}
	return arr[arr.length-1];
}
//Time complexity: O(K). Space Complexity: O(K)

you_ser =[4,7,44,47,74,77]
lucky_num = input('Enter your lucky number : ')
if you_ser.idex(lucky_num):
print(you_ser[you_ser.idex(lucky_num)])
else:
print('Enter number in 4,7,44,47,74,77')

sdfasdf

it is codeforces question