Examine the following code blocks and give the Big-Oh run time of the code blocks in simplest terms of n (with coefficients of 1 and lower-order terms dropped out e.g. O(n) not O(2n+1)).

1. for(int i = 1; i < n; i++) sum++; 

2. for(int i = 1; i < n; i++) { if( i % 2 == 0 ) { array[i] = 0; } else { for( int j = 0; j < n/2; j++ ) { array[j] = 1; } } } 

3. for(int i = n; i > 0; i = i / 3) sum++; 

4. for(int i = n; i > 0; i = i / 3) for( int j = i; j < n; j++ ) sum++;