hello-algo/codes/java/chapter_backtracking/preorder_traversal_iii_compact.java

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/**
* File: preorder_traversal_iii_compact.java
* Created Time: 2023-04-16
* Author: Krahets (krahets@163.com)
*/
package chapter_backtracking;
import utils.*;
import java.util.*;
public class preorder_traversal_iii_compact {
static List<TreeNode> path;
static List<List<TreeNode>> res;
/* 前序遍历:例题三 */
static void preOrder(TreeNode root) {
// 剪枝
if (root == null || root.val == 3) {
return;
}
// 尝试
path.add(root);
if (root.val == 7) {
// 记录解
res.add(new ArrayList<>(path));
path.remove(path.size() - 1);
return;
}
preOrder(root.left);
preOrder(root.right);
// 回退
path.remove(path.size() - 1);
}
public static void main(String[] args) {
TreeNode root = TreeNode.listToTree(Arrays.asList(1, 7, 3, 4, 5, 6, 7));
System.out.println("\n初始化二叉树");
PrintUtil.printTree(root);
// 前序遍历
path = new ArrayList<>();
res = new ArrayList<>();
preOrder(root);
System.out.println("\n输出所有根节点到节点 7 的路径,路径中不包含值为 3 的节点,仅包含一个值为 7 的节点");
for (List<TreeNode> path : res) {
List<Integer> vals = new ArrayList<>();
for (TreeNode node : path) {
vals.add(node.val);
}
System.out.println(vals);
}
}
}