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Code05_MaxSubBSTSize.java
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157 lines (142 loc) · 3.76 KB
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package class12;
import java.util.ArrayList;
// 在线测试链接 : https://leetcode.com/problems/largest-bst-subtree
public class Code05_MaxSubBSTSize {
// 提交时不要提交这个类
public static class TreeNode {
public int val;
public TreeNode left;
public TreeNode right;
public TreeNode(int value) {
val = value;
}
}
// 提交如下的largestBSTSubtree方法，可以直接通过
public static int largestBSTSubtree(TreeNode head) {
if (head == null) {
return 0;
}
return process(head).maxBSTSubtreeSize;
}
public static class Info {
public int maxBSTSubtreeSize;
public int allSize;
public int max;
public int min;
public Info(int m, int a, int ma, int mi) {
maxBSTSubtreeSize = m;
allSize = a;
max = ma;
min = mi;
}
}
public static Info process(TreeNode x) {
if (x == null) {
return null;
}
Info leftInfo = process(x.left);
Info rightInfo = process(x.right);
int max = x.val;
int min = x.val;
int allSize = 1;
if (leftInfo != null) {
max = Math.max(leftInfo.max, max);
min = Math.min(leftInfo.min, min);
allSize += leftInfo.allSize;
}
if (rightInfo != null) {
max = Math.max(rightInfo.max, max);
min = Math.min(rightInfo.min, min);
allSize += rightInfo.allSize;
}
int p1 = -1;
if (leftInfo != null) {
p1 = leftInfo.maxBSTSubtreeSize;
}
int p2 = -1;
if (rightInfo != null) {
p2 = rightInfo.maxBSTSubtreeSize;
}
int p3 = -1;
boolean leftBST = leftInfo == null ? true : (leftInfo.maxBSTSubtreeSize == leftInfo.allSize);
boolean rightBST = rightInfo == null ? true : (rightInfo.maxBSTSubtreeSize == rightInfo.allSize);
if (leftBST && rightBST) {
boolean leftMaxLessX = leftInfo == null ? true : (leftInfo.max < x.val);
boolean rightMinMoreX = rightInfo == null ? true : (x.val < rightInfo.min);
if (leftMaxLessX && rightMinMoreX) {
int leftSize = leftInfo == null ? 0 : leftInfo.allSize;
int rightSize = rightInfo == null ? 0 : rightInfo.allSize;
p3 = leftSize + rightSize + 1;
}
}
return new Info(Math.max(p1, Math.max(p2, p3)), allSize, max, min);
}
// 为了验证
// 对数器方法
public static int right(TreeNode head) {
if (head == null) {
return 0;
}
int h = getBSTSize(head);
if (h != 0) {
return h;
}
return Math.max(right(head.left), right(head.right));
}
// 为了验证
// 对数器方法
public static int getBSTSize(TreeNode head) {
if (head == null) {
return 0;
}
ArrayList<TreeNode> arr = new ArrayList<>();
in(head, arr);
for (int i = 1; i < arr.size(); i++) {
if (arr.get(i).val <= arr.get(i - 1).val) {
return 0;
}
}
return arr.size();
}
// 为了验证
// 对数器方法
public static void in(TreeNode head, ArrayList<TreeNode> arr) {
if (head == null) {
return;
}
in(head.left, arr);
arr.add(head);
in(head.right, arr);
}
// 为了验证
// 对数器方法
public static TreeNode generateRandomBST(int maxLevel, int maxValue) {
return generate(1, maxLevel, maxValue);
}
// 为了验证
// 对数器方法
public static TreeNode generate(int level, int maxLevel, int maxValue) {
if (level > maxLevel || Math.random() < 0.5) {
return null;
}
TreeNode head = new TreeNode((int) (Math.random() * maxValue));
head.left = generate(level + 1, maxLevel, maxValue);
head.right = generate(level + 1, maxLevel, maxValue);
return head;
}
// 为了验证
// 对数器方法
public static void main(String[] args) {
int maxLevel = 4;
int maxValue = 100;
int testTimes = 1000000;
System.out.println("测试开始");
for (int i = 0; i < testTimes; i++) {
TreeNode head = generateRandomBST(maxLevel, maxValue);
if (largestBSTSubtree(head) != right(head)) {
System.out.println("出错了！");
}
}
System.out.println("测试结束");
}
}