Time complexity

Question

What is  the time complexity of the following code?
 

int j = 0;
for(i=0;i<n;i++)
    {
    for(i=0;i<2n;i++)
        {
        while(j<n)  
            {
              j++;
            }
        }
    }

a) O(n$^{4}$)

b) O(n$^{3}$)

c) O(n$^{2}$)

d) O(n)

I am getting option O(n$^{2}$)  and answer is given O(n)

Explain briefly.

Comments

@Na462 @srestha Yes, It's $O(n^2)$ :)

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@Soumya

here TC of j is O(1) right?

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 srestha  Soumya29 

Both of them are taking variable 'i' but it is not a global variable. It is local within its scope. So, the complexity should be O(n²)

Answer 1

o(n²) is correct