com.link_intersystems.graph.tree.DepthFirstBottomUpTreeModelIterable Maven / Gradle / Ivy
Show all versions of lis-commons-graph Show documentation
package com.link_intersystems.graph.tree;
import java.util.*;
import java.util.stream.Stream;
/**
* Iterates through a tree model by depth first strategy, but returns the elements in reverse order of the branches.
*
* Assume the following tree structure. The number show the iteration order.
*
*
*
* +-(2)--(1)
* |
* (7)-+-(3)
* |
* | +-(4)
* | |
* +-(6)-+
* |
* +-(5)
*
*
* You can {@link #setLeavesOnly(boolean)} to true and it will only iterate the leaves: 1, 4, 5.
*
* @author René Link {@literal }
*/
public class DepthFirstBottomUpTreeModelIterable extends AbstractTreeModelIterable {
private boolean leavesOnly;
public DepthFirstBottomUpTreeModelIterable(TreeModel treeModel, T rootElement) {
super(treeModel, rootElement);
}
public void setLeavesOnly(boolean leavesOnly) {
this.leavesOnly = leavesOnly;
}
@Override
protected Iterator createIterator(TreeModel treeModel, T rootElement) {
Stack stack = new Stack<>();
stack.push(rootElement);
Set childrenResolved = Collections.newSetFromMap(new IdentityHashMap<>());
Map isLeaf = new IdentityHashMap<>();
return new Iterator() {
@Override
public boolean hasNext() {
return !stack.isEmpty();
}
@Override
public T next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
while (true) {
T head = stack.peek();
if (childrenResolved.contains(head)) {
break;
}
Stream children = treeModel.getChildren(head);
int headIndex = stack.size();
children.forEach(c -> stack.add(headIndex, c));
childrenResolved.add(head);
boolean stackNotModified = headIndex == stack.size();
isLeaf.put(head, stackNotModified);
if (stackNotModified) {
break;
} else {
if (leavesOnly) stack.remove(headIndex - 1);
}
}
T next = stack.pop();
return next;
}
};
}
}