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90 lines
1.9 KiB
90 lines
1.9 KiB
package class_2021_11_4_week;
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import java.util.ArrayList;
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import java.util.List;
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public class Code01_RetainTree {
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public static class Node {
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// 值
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public int value;
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// 是否保留
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public boolean retain;
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// 下级节点
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public List<Node> nexts;
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public Node(int v, boolean r) {
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value = v;
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retain = r;
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nexts = new ArrayList<>();
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}
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}
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// 给定一棵树的头节点head
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// 请按照题意，保留节点，没有保留的节点删掉
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// 树调整完之后，返回头节点
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public static Node retain(Node x) {
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if (x.nexts.isEmpty()) {
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return x.retain ? x : null;
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}
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// x下层有节点
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List<Node> newNexts = new ArrayList<>();
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for (Node next : x.nexts) {
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Node newNext = retain(next);
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if (newNext != null) {
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newNexts.add(newNext);
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}
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}
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// x.nexts 老的链表，下级节点
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// newNexts 新的链表，只有保留的在里面
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//
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if (!newNexts.isEmpty() || x.retain) {
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x.nexts = newNexts;
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return x;
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}
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return null;
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}
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// 先序打印
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public static void preOrderPrint(Node head) {
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System.out.println(head.value);
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for (Node next : head.nexts) {
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preOrderPrint(next);
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}
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}
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public static void main(String[] args) {
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Node n1 = new Node(1, false);
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Node n2 = new Node(2, true);
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Node n3 = new Node(3, false);
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Node n4 = new Node(4, false);
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Node n5 = new Node(5, false);
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Node n6 = new Node(6, true);
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Node n7 = new Node(7, true);
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Node n8 = new Node(8, false);
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Node n9 = new Node(9, false);
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Node n10 = new Node(10, false);
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Node n11 = new Node(11, false);
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Node n12 = new Node(12, false);
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Node n13 = new Node(13, true);
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n1.nexts.add(n2);
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n1.nexts.add(n3);
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n2.nexts.add(n4);
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n2.nexts.add(n5);
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n3.nexts.add(n6);
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n3.nexts.add(n7);
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n6.nexts.add(n8);
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n6.nexts.add(n9);
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n6.nexts.add(n10);
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n7.nexts.add(n11);
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n7.nexts.add(n12);
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n9.nexts.add(n13);
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Node head = retain(n1);
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preOrderPrint(head);
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}
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}
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