Question

Please DONOT attempt this Big O question if you don't know the exact answer.

Algorithms question (Big O): Please explain me in details the order of growth (as a function of N) of the running times of each of the following code fragments:

a)         int sum = 0;

for (int n = N; n > 0; n /= 2)

   for(int i = 0; i < n; i++)

     sum++;

b)         int sum = 0;

for (int i = 1 i < N; i *= 2)

     for (int j = 0; j < i; j++)

          sum++;

c)         int sum = 0;

for (int i = 1 i < N; i *= 2)

for (int j = 0; j < N; j++)

      sum++;

Note: No copy/paste from Google search please. Send me the answer only if you have very clear concept on this