Determine the BigO Complexity

(Q17) for (i = j = 1; j < n; j += i, i++)

// some O(1) expression

(Q18) int i = 0;

for (int j = 0; j < n; j*=2)

i++;

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

// some O(1) expression

(Q19) int i = 0;

for (int j = 0; i < n; j++)

i += j;

(Q20) for (int i = n; i > 0; i /= 2)

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

(Q21) while (m != n){

if (m > n)

m = m n;

else

n = n m;

}