java最长路径算法_求二叉树的一条最长路径
题目 输入一颗二叉树和一个整数，打印出二叉树中结点值的和为输入整数的所有路径。路径定义为从树的根结点开始往下一直到叶结点所经过的结点形成一条路径。 解题 求根结点到叶子结点的路径，这个路径的和等于target 深度优先 这里结点有左右两个子树，故要分
import java.util.*;
public class BinaryTree {
protected Node root;
public BinaryTree(Node root) {
this.root = root;
}
public Node getRoot() {
return root;
}
/** 构造树 */
public static Node init() {
Node a = new Node('A');
Node b = new Node('B', null, a);
Node c = new Node('C');
Node d = new Node('D', b, c);
Node i = new Node('I');
Node e = new Node('E',i,null);
Node f = new Node('F', e, null);
Node g = new Node('G', null, f);
Node h = new Node('H', d, g);
return h;// root
}
/** 访问节点 */
public static void visit(Node p) {
System.out.print(p.getKey() + " ");
}
// 求二叉树的高度
static int height(Node tree) {
if (tree == null)
return 0;
else {
int leftTreeHeight = height(tree.getLeft());
int rightTreeHeight = height(tree.getRight());;
return leftTreeHeight > rightTreeHeight ? leftTreeHeight + 1: rightTreeHeight + 1;
}
}
// 求二叉树的结点总数
static int nodes(Node tree) {
if (tree == null)
return 0;
else {
int left = nodes(tree.getLeft());
int right = nodes(tree.getRight());
return left + right + 1;
}
}
// 求二叉树叶子节点的总数
static int leaf(Node tree) {
if (tree == null)
return 0;
else {
int left = leaf(tree.getLeft());
int right = leaf(tree.getRight());
if (tree.getLeft() == null && tree.getRight() == null)
return left + right + 1;
else
return left + right;
}
}
//将二叉树所有结点的左右子树交换
static void swapTree(Node root){
if(root != null) {
Node tmp = root.getLeft();
root.setLeft(root.getRight());
root.setRight(tmp);
swapTree(root.getLeft());
swapTree(root.getRight());
}
}
/**
* getLeafNodes: 递归求解给定二叉树的所有叶子结点
* @param root 给定二叉树的根结点
* @param leaflist 给定二叉树的所有叶子结点
*/
static void getLeafNodes(Node root, List leaflist)
{
if (root != null) {
if (root.getLeft() == null && root.getRight() == null) {
leaflist.add(root);
return ;
}
getLeafNodes(root.getLeft(), leaflist);
getLeafNodes(root.getRight(), leaflist);
}
}
/**
* longestPath: 递归求解给定二叉树的一条最长路径 如果有多条，输出其中一条
* @param root 给定二叉树的根结点
* @param longestPath 存放二叉树的最长路径上的结点
*/
static void longestPath(Node root, List longestPath)
{
if (root != null) {
longestPath.add(root);
if (root.getLeft() == null && root.getRight() == null) { // 左右子树均空
return ;
}
List leftLongestPath = new ArrayList();
List rightLongestPath = new ArrayList();
longestPath(root.getLeft(), leftLongestPath);
longestPath(root.getRight(), rightLongestPath);
if (leftLongestPath.size() >= rightLongestPath.size()) {
longestPath.addAll(leftLongestPath);
} else if (leftLongestPath.size() < rightLongestPath.size()) {
longestPath.addAll(rightLongestPath);
}
}
}
/**
* @param args
*/
public static void main(String[] args) {
BinaryTree tree = new BinaryTree(init());
System.out.println("叶子结点数");
System.out.println(leaf(tree.getRoot()));
System.out.println("总结点数");
System.out.println(nodes(tree.getRoot()));
System.out.println("树的高度");
System.out.println(height(tree.getRoot()));
System.out.println();
System.out.println("一条最长路径");
List l=new ArrayList();
longestPath(tree.getRoot(),l);
for(int i=0;i
System.out.println(l.get(i).getKey());
}
}
public class Node {
private char key;
private Node left, right;
public Node(char key) {
this(key, null, null);
}
public Node(char key, Node left, Node right) {
this.key = key;
this.left = left;
this.right = right;
}
public char getKey() {
return key;
}
public void setKey(char key) {
this.key = key;
}
public Node getLeft() {
return left;
}
public void setLeft(Node left) {
this.left = left;
}
public Node getRight() {
return right;
}
public void setRight(Node right) {
this.right = right;
}
}
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