for (gap = n/2; gap > 0; gap /= 2) without a ";" at its end

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I read the following codes in "The C programming language edition 2"

/* shellsort: sort v[0] ... v[n-1] into increasing order */
void shellsort(int v[], int n) {
    int gap, i, j, temp;

    for (gap = n/2; gap > 0; gap /= 2) 
        for (i = gap; i < n; i++)
            for (j=i-gap; j>=0 && v[j]>v[j+gap]; j-=gap) {
                temp = v[j];
                v[j] = v[j+gap];
                v[j+gap] = temp;
            }

}

What confuse me is that there's no ";" at the end of "for loop line", I assume it should be

    for (gap = n/2; gap > 0; gap /= 2) ;
        for (i = gap; i < n; i++);
            for (j=i-gap; j>=0 && v[j]>v[j+gap]; j-=gap) {
                temp = v[j];
                v[j] = v[j+gap];
                v[j+gap] = temp;
            }

How could I wrap it around intuitively?

The syntax of the for loop is (simplified for clarity):

for ( ... ) <statement>

statement:
     ';'  // empty statement
      <any other statement>
     '{' ... '}'  // block of statements

So following the for statement comes one statement or a block of statement. And a single ; is a statement, namely the empty (do nothing) statement. So

for (....) ;
    for (....) ;

is not a nested for-loop. It is equivalent to:

for (....) ;
for (....) ;

or

for (....) {}
for (....) {}

Figure 8 shows a final insertion sort using an increment of one; in other words, a standard insertion sort. Note that by In this case, we begin with n2 sublists. On the next pass, n4 while position>=gap and alist[position-gap]>currentvalue: 20. The problem is that GAP, like lots of computer scientists, treats mod n as a unary suffix operator that returns the canonical representative mod n of its argument. For example, gap> 2 = 0 mod 2; #GAP thinks you are testing 2 = 0 false gap> (2 mod 2) = 0; true. Also, you missed out the 5 r condition from (a). share.

The statement

for (gap = n/2; gap > 0; gap /= 2) ;

is equal to

for (gap = n/2; gap > 0; gap /= 2)
    ;

which is equal to

for (gap = n/2; gap > 0; gap /= 2)
{
}

In other words, that's an empty loop that does nothing except the comparison gap > 0 and gap /= 2 (part of the loop) each iteration.

void shellsort(table, n) tabletype table[]; int n;. { int gap, i, j; tabletype temp; for (​gap = n/2; gap > 0; gap = gap/2) for (i = gap; i < n; i++) for (j = i-gap;. Time Complexity: Time complexity of above implementation of shellsort is O(n 2). In the above implementation gap is reduce by half in every iteration. In the above implementation gap is reduce by half in every iteration.

The for loop runs the next statement in the code the appropriate number of times. Often this statement is a single statement, or a group of statements in curly brackets. If you put a semicolon instead, it's treated as a null statement, and so "nothing" is done the appropriate number of times.

If you explain what you mean when you say "How could I wrap it around intuitively?" that might make it easier to answer your question.

4.2.5 Parity gap In this subsection, we consider a parity gap in the case of of occupied levels corresponding to each sublevel are n1 and n2, respectively. Then  Since gap is always 5 and j increments from 0,1,2,3,4 that means the first 5 times this inner for loop runs, it will return a negative value to j (e.g. 0-5=-5), and thus since j will not be greater than or equal to 0, it will only run once. That's exactly what we want.

A peculiar feature of Fermi superfluids is the occurrence of a gap Δgap in the system according to the relationship E(N/2 ± 1, N/2) = E(N/2, N/2) ± μ + Δgap. Find an answer to your question Between what two data values is there the largest gap? 1/16 and 3/16 3/16 and 3/8 3/8 and 1/2 1/2 and 5/8

Thus, for neutrons we get the shell gaps not only at N=2, 8, 14, 20 and 28 but also at N=6, 10 and 18 (the gap at N=18 is small but is almost as wide as at N=20​). The anion gap value is the difference between the negatively and positively charged electrolytes. If the calculated value for the anion gap is too high or too low, it may be a sign of a disorder

Sort an array a[0n-1]. gaps = [701, 301, 132, 57, 23, 10, 4, 1] # Start with the Worst case time complexity: Θ(N (log N)^2) comparisons; Average case time  In the above implementation of shell sort time complexity in the worst case is O(n 2) as gap reduces by half in every iteration. To get better time complexity we can choose some other gap sequence as discussed above.

Comments
  • A ; after the for() statement means the body of the loop is an empty statement. The formatting makes it assume it is a nested for loop but it is not. First the first for loop is completely executed and only then will next for loop start.
  • Since no one has said it explicitly: your assumption is wrong, and the book is correct. If you place ; characters where you propose, the code will no longer perform a shell sort, because the outer loops will run without any body and the inner loop will only run once.
  • Surely what you are really confused about is that there is no { after the for-statement. Lots of programmers think there should be, even though it isn't necessary. Count yourself part of that group, you wouldn't have asked the question if it were there.
  • @HansPassant Yeah, damned braces spammers ... those guys paid by #LOCs. Disgusting!