Understanding Big-O, due Wednesday, 8/29

For each of the following snippets of code, what is the Big-O of the worst case for that algorithm?

  1.   for (int i = 0; i < n; i++)
    sum++;
  
  2.   for (int i = 0; i < n*n; i++)
    sum++;
  
  3.   for (int i = 0; i < n; i++)
    for (int j = i; j < n; j++)
      sum++;
  
  4.   for (int i = 0; i < n; i++)
    for (int j = 0; j < i; j++)
      sum++;
  
  5.   for (int i = 0; i < n; i++)
    for (int j = 5; j < n; j++)
      sum++;
  
  6.   for (int i = 0; i < n; i++)
    for (int j = 1; j < n; j*=2)
      sum++;
  
  7.   for (int i = 0; i < n; i*=2)
    for (int j = 1; j < n; j++)
      sum++;
  
  8.   for (int i = 0; i < n; i*=2)
    for (int j = 1; j < n*n; j++)
      for (int k = 0; k < j; k++)
        sum++;