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Code01_IsCBT.java
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149 lines (124 loc) · 3.04 KB
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package class12;
import java.util.LinkedList;
public class Code01_IsCBT {
public static class Node {
public int value;
public Node left;
public Node right;
public Node(int data) {
this.value = data;
}
}
public static boolean isCBT1(Node head) {
if (head == null) {
return true;
}
LinkedList<Node> queue = new LinkedList<>();
// 是否遇到过左右两个孩子不双全的节点
boolean leaf = false;
Node l = null;
Node r = null;
queue.add(head);
while (!queue.isEmpty()) {
head = queue.poll();
l = head.left;
r = head.right;
if (
// 如果遇到了不双全的节点之后，又发现当前节点不是叶节点
(leaf && (l != null || r != null))
||
(l == null && r != null)
) {
return false;
}
if (l != null) {
queue.add(l);
}
if (r != null) {
queue.add(r);
}
if (l == null || r == null) {
leaf = true;
}
}
return true;
}
public static boolean isCBT2(Node head) {
if (head == null) {
return true;
}
return process(head).isCBT;
}
// 对每一棵子树，是否是满二叉树、是否是完全二叉树、高度
public static class Info {
public boolean isFull;
public boolean isCBT;
public int height;
public Info(boolean full, boolean cbt, int h) {
isFull = full;
isCBT = cbt;
height = h;
}
}
public static Info process(Node X) {
if (X == null) {
return new Info(true, true, 0);
}
Info leftInfo = process(X.left);
Info rightInfo = process(X.right);
int height = Math.max(leftInfo.height, rightInfo.height) + 1;
boolean isFull = leftInfo.isFull
&&
rightInfo.isFull
&& leftInfo.height == rightInfo.height;
boolean isCBT = false;
if (isFull) {
isCBT = true;
} else { // 以x为头整棵树，不满
if (leftInfo.isCBT && rightInfo.isCBT) {
if (leftInfo.isCBT
&& rightInfo.isFull
&& leftInfo.height == rightInfo.height + 1) {
isCBT = true;
}
if (leftInfo.isFull
&&
rightInfo.isFull
&& leftInfo.height == rightInfo.height + 1) {
isCBT = true;
}
if (leftInfo.isFull
&& rightInfo.isCBT && leftInfo.height == rightInfo.height) {
isCBT = true;
}
}
}
return new Info(isFull, isCBT, height);
}
// for test
public static Node generateRandomBST(int maxLevel, int maxValue) {
return generate(1, maxLevel, maxValue);
}
// for test
public static Node generate(int level, int maxLevel, int maxValue) {
if (level > maxLevel || Math.random() < 0.5) {
return null;
}
Node head = new Node((int) (Math.random() * maxValue));
head.left = generate(level + 1, maxLevel, maxValue);
head.right = generate(level + 1, maxLevel, maxValue);
return head;
}
public static void main(String[] args) {
int maxLevel = 5;
int maxValue = 100;
int testTimes = 1000000;
for (int i = 0; i < testTimes; i++) {
Node head = generateRandomBST(maxLevel, maxValue);
if (isCBT1(head) != isCBT2(head)) {
System.out.println("Oops!");
}
}
System.out.println("finish!");
}
}