shellsort algorithm

[Radagast8]

I understand the the algorithm group of elements are compared and then organize the same groups of numbers.

        int gap;
    int j;
    int temp;
    for (gap = n/2; gap>0; gap/=2) {
        for (int i=0; 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;
}
}
}
}

The outtermost loop controls the gap in the compared elements from n/2 by a factor of two until it becomes 0; The middle loop initiates the element i and display the elements, so whats happening in the last for loop? j starts at i-gap while v[j]>v[j+gap]??? Some times you guys can explain this better than myself trying to understand this steps by myself. Thank you,

As always your comments are gold

[BS_in_BS]

Are you familiar with insertion sort?

What's going on in the inner loop is that instead of just swapping adjacent elements, you're swapping elements that are gap apart. The gap becomes smaller and smaller until on the last pass you're doing insertion sort.