Batuhan Aydın - 3 months ago 48

C# Question

As I checked, I find the right minimum value and previous node.After that the only thing I need to do is swapping nodes.However, after implementing this code the output is nothing.

After drawing the question I thought the problem is sorted part.So I added one more node which name is sorted but still I couldn't solve my problem.

`public void selectionSort()`

{

Node<T> first = head;

Node<T> previous = head;

Node<T> minimum = head;

Node<T> compare;

Node<T> temp;

Node<T> sorted = head;

while (first.Next != null)

{

sorted = minimum; // with this I'm finding the last sorted node

minimum = first;

compare = first.Next;

while (compare.Next != null)

{

if (minimum.Value.CompareTo(compare.Next.Value) > 0)

{

previous = compare; // Need previous node to changing connections

minimum = compare.Next; // Saving minimum value

}

compare = compare.Next;

}

// Swapping nodes

temp = first;

previous.Next = first;

first.Next = minimum.Next;

minimum.Next = temp.Next;

if ( temp != head)

{

sorted.Next = minimum; // Adding minimum node to sorted part

}

first = first.Next;

}

}

Answer

I renamed the variables from your code to more meaningful ones:

`currentOuter`

tracks the current node in the outer loop`previousCurrentOuter`

tracks the previous node of the current node in the outer loop`currentInner`

tracks the current node in the inner loop`previousCurrentInner`

tracks the previous node of the current node in the inner loop`minimum`

tracks the minimum node`previousMinimum`

tracks the node previous to the minimum node

`previousMinimum`

, `previousCurrentOuter`

, `minimum`

and `currentOuter`

are required for the swapping process.

`previousCurrentInner`

or `previousCurrentOuter`

are needed to determine the `previousMinimum`

node: if the minimum doesn't correspond to the current element in the outer loop, then `previousCurrentInner`

is used, otherwise `previousCurrentOuter`

.

**Code**:

```
public void selectionSort<T>() where T:IComparable
{
Node<T> currentOuter = head;
Node<T> previousCurrentOuter = null;
Node<T> minimum;
Node<T> previousMinimum = null;
while (currentOuter != null) {
minimum = currentOuter;
Node<T> previousCurrentInner = currentOuter;
Node<T> currentInner = currentOuter.Next;
while (currentInner != null) {
if (currentInner.Value.CompareTo(minimum.Value) < 0) {
minimum = currentInner;
previousMinimum = previousCurrentInner;
}
previousCurrentInner = currentInner;
currentInner = currentInner.Next;
}
if (!Object.ReferenceEquals(minimum, currentOuter)) {
Node<T> temp = minimum.Next;
if (previousMinimum.Next != null) previousMinimum.Next = currentOuter;
if (previousCurrentOuter != null) previousCurrentOuter.Next = minimum;
minimum.Next = currentOuter.Next;
currentOuter.Next = temp;
}
previousCurrentOuter = currentOuter;
previousMinimum = currentOuter;
currentOuter = currentOuter.Next;
}
}
```