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PathToEveryLeaf.java
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PathToEveryLeaf.java
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/*
* Copyright (C) 2014 Pedro Vicente Gómez Sánchez.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.github.pedrovgs.problem38;
import com.github.pedrovgs.binarytree.BinaryNode;
import java.util.LinkedList;
import java.util.List;
/**
* Given a binary tree, can you write a method to calculate every path to every leaf in the tree.
*
* @author Pedro Vicente Gómez Sánchez.
*/
public class PathToEveryLeaf {
/**
* Recursive algorithm to solve this problem. The complexity order of this algorithm is O(N)
* where N is the number of elements in the array in time and space terms.
*/
public List<List<BinaryNode>> calculate(BinaryNode<Integer> root) {
if (root == null) {
throw new IllegalArgumentException("You can't pass a null instance of BinaryNode");
}
return calculatePathToLeafs(root, new LinkedList<BinaryNode>());
}
private static List<List<BinaryNode>> calculatePathToLeafs(BinaryNode<Integer> root,
List<BinaryNode> path) {
List<List<BinaryNode>> paths = new LinkedList<List<BinaryNode>>();
if (root == null) {
return paths;
} else if (root.getLeft() == null && root.getRight() == null) {
path.add(root);
paths.add(path);
return paths;
} else {
path.add(root);
paths.addAll(calculatePathToLeafs(root.getLeft(), new LinkedList<BinaryNode>(path)));
paths.addAll(calculatePathToLeafs(root.getRight(), new LinkedList<BinaryNode>(path)));
return paths;
}
}
}