why is this n(square) complexity?

Question

why is this code n^2 complexity when there are three for loops? and how do u tell the different complexity of the code? here is the code:

    int size1= sc.nextInt();
    int size2 = sc.nextInt();

    int value=0;
    for(int k=0;k<size1;k++)
    {
        value++;
        //5 times
        for(int x=0;x<size2;x++)
        {
            value++;
            //15 times
            for(int i=0;i<x;i++)
            {
                value++;
                //15 times
            }
        }
    }


    System.out.println(value);

}

Answer 1

The complexity of your code is O(n^3) if we assume that n=size1=size2.

If only size2=n and size1=k (small constant), the complexity is O(kn^2), which is O(n^2) if we only consider the variable n to be large.

Answer 2

I think you mean complexity not efficiency. The reason this is O(nˆ2) is that it has quadratic complexity because the third loop uses the second variable.

More info here .