二叉树节点和+递归Java_二叉树根节点到叶子结点的路径:递归与非递归
package 二叉树;
import java.util.*;
public class 二叉树根到叶子节点的路径和 {
public static TreeNode root;
public static Set> set = new HashSet<>();
public static List list = new ArrayList<>();
public static List sum = new ArrayList<>();
public static void createTree(Integer[] objects){
List datas = new ArrayList<>();//存储所有节点
for(Integer obj:objects){
datas.add(new TreeNode(obj));
}
root = datas.get(0);//将一个作为根节点
for(int i = 0;i < objects.length/2;i++){
datas.get(i).left = datas.get(2*i+1);
if(2*i+2 < objects.length){//避免偶数的时候，下标越界
datas.get(i).right = datas.get(2*i+2);
}
}
}
public static void DFS(TreeNode T,int preVal,List list){
if(T!=null){
preVal+=T.val;
list.add(T.val);
if(T.left==null&&T.right==null){
System.out.println(list);
set.add(new ArrayList<>(list));
sum.add(preVal);
}else{
DFS(T.left,preVal,list);
DFS(T.right,preVal,list);
}
//当T是叶子节点，在当前递归状态下需要剔除该元素
list.remove(list.size()-1);
}
}
public static void getPath(TreeNode root,List list,int num){
if(root!=null) {
num+=root.val;
list.add(root.val);
}
if(root.left == null && root.right == null){
System.out.print(num+"=");
System.out.println(list);
sum.add(num);
set.add(new ArrayList<>(list));
}
if(root.left != null)
getPath(root.left,list,num);
if(root.right != null)
getPath(root.right,list,num);
list.remove(list.size()-1);
}
public static List binaryTreePaths(TreeNode root) {
List list=new ArrayList();
Queue queue=new LinkedList();
Queue qStr=new LinkedList();
if (root==null) return list;
queue.add(root);
qStr.add("");
while(!queue.isEmpty()) {
TreeNode curNode=queue.remove();
String curStr=qStr.remove();
if (curNode.left==null && curNode.right==null) list.add(curStr+curNode.val);
if (curNode.left!=null) {
queue.add(curNode.left);
qStr.add(curStr+curNode.val+"->");
}
if (curNode.right!=null) {
queue.add(curNode.right);
qStr.add(curStr+curNode.val+"->");
}
}
return list;
}
public static void main(String[] args) {
Integer[] arr = {1,3,2,4,5,2,1};
createTree(arr);
DFS(root,0,list);
sum.clear();
getPath(root,list,0);
System.out.println(sum);
System.out.println(set);
System.out.println(binaryTreePaths(root));
}
}