java - O-notation with for-loop with modulo condition -


my question how calculate o-notation operation, 2 outer loops go o(n^3) times. question o-notation going when modulo used in condtion , inner for-loop runs when factor in j.

for(int = 1 ; <= n ; i++) {    for(int j =1; j <= ∗ ; j++) {       if(j % == 0 ) {          for(int k = 0 ; k < j ; k++ ){              sum++;          }        }     } } 

it o(n^4).

the trick 1 if (j % == 0). since i pretty n , j going range n^2 know statement true n + (n-1) + ... + 1 times going simplify (n+1)(n+2)/2 or o(n^2) in turn run loop runs n^2 times. need treat addition, have n^3 + n^2 * n^2, simplifies o(n^4).

if there fault in reasoning please point out, little rusty.


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