// links y under x
private void link(FibonacciHeapNode y, FibonacciHeapNode x) {
removeFromSiblings(y);
y.parent = x;
if (x.child == null) x.child = y;
else concatenateSiblings(x.child, y);
x.degree++;
y.mark = false;
}
// cut node x from below y
private void cut(FibonacciHeapNode x, FibonacciHeapNode y) {
// remove x from y's children
if (y.child == x) y.child = x.nextSibling;
if (y.child == x) y.child = null;
y.degree--;
removeFromSiblings(x);
concatenateSiblings(x, min);
x.parent = null;
x.mark = false;
}
/**
* Returns the object which has the <em>lowest</em> priority in the heap. If the heap is empty,
* <code>null</code> is returned.
*/
public Object popMin() {
if (min == null) return null;
if (min.child != null) {
FibonacciHeapNode tmp = min.child;
// rempve parent pointers to min
while (tmp.parent != null) {
tmp.parent = null;
tmp = tmp.nextSibling;
}
// add children of min to root list
concatenateSiblings(tmp, min);
}
// remove min from root list
FibonacciHeapNode oldMin = min;
if (min.nextSibling == min) {
min = null;
} else {
min = min.nextSibling;
removeFromSiblings(oldMin);
consolidate();
}
itemsToNodes.remove(oldMin.userObject);
return oldMin.userObject;
}
