I was just working on a problem and I can't understand why one of my solutions passed and the other didn't.

I have two loops that are the same complexity. Since they are the same complexity, it should simplify to O(N)+O(N)=O(2N) which just becomes O(N). When I take out one of the loops, my solution passes, but when I keep them both in I get TLE. I don't understand this since they should simplify to the same complexity. Can someone please help?

Not accepted solution:

while(number>0){

if(number % 2==0){

stack.add(1);

}

else{

stack.add(2);

}

number/=2;

}

int originalsize= stack.size();

for (int i = 0; i < originalsize; i++) {

System.out.print(stack.pop()+ " ");

}

Accepted solution:

String ans="";

while(number>0){

if(number % 2==0){

ans="1 "+ans;

}

else{

ans="2 "+ans;

}

number/=2;

}

System.out.println(ans);

Problem link: https://mirror.codeforces.com/contest/1810/problem/B Accepted Solution: https://mirror.codeforces.com/contest/1810/submission/207920289 Not accepted Solution: https://mirror.codeforces.com/contest/1810/submission/207919439