package chapter_3_binarytreeproblem;
public class Problem_07_BiggestSubBSTInTree {
public static class Node {
public int value;
public Node left;
public Node right;
public Node(int data) {
this.value = data;
}
}
public static Node biggestSubBST(Node head) {
int[] record = new int[3]; // 0->size, 1->min, 2->max
return posOrder(head, record);
}
public static Node posOrder(Node head, int[] record) {
if (head == null) {
record[0] = 0;
record[1] = Integer.MAX_VALUE;
record[2] = Integer.MIN_VALUE;
return null;
}
int value = head.value;
Node left = head.left;
Node right = head.right;
Node lBST = posOrder(left, record);
int lSize = record[0];
int lMin = record[1];
int lMax = record[2];
Node rBST = posOrder(right, record);
int rSize = record[0];
int rMin = record[1];
int rMax = record[2];
record[1] = Math.min(lMin, value);
record[2] = Math.max(rMax, value);
if (left == lBST && right == rBST && lMax < value && value < rMin) {
record[0] = lSize + rSize + 1;
return head;
}
record[0] = Math.max(lSize, rSize);
return lSize > rSize ? lBST : rBST;
}
// for test -- print tree
public static void printTree(Node head) {
System.out.println("Binary Tree:");
printInOrder(head, 0, "H", 17);
System.out.println();
}
public static void printInOrder(Node head, int height, String to, int len) {
if (head == null) {
return;
}
printInOrder(head.right, height + 1, "v", len);
String val = to + head.value + to;
int lenM = val.length();
int lenL = (len - lenM) / 2;
int lenR = len - lenM - lenL;
val = getSpace(lenL) + val + getSpace(lenR);
System.out.println(getSpace(height * len) + val);
printInOrder(head.left, height + 1, "^", len);
}
public static String getSpace(int num) {
String space = " ";
StringBuffer buf = new StringBuffer("");
for (int i = 0; i < num; i++) {
buf.append(space);
}
return buf.toString();
}
public static void main(String[] args) {
Node head = new Node(6);
head.left = new Node(1);
head.left.left = new Node(0);
head.left.right = new Node(3);
head.right = new Node(12);
head.right.left = new Node(10);
head.right.left.left = new Node(4);
head.right.left.left.left = new Node(2);
head.right.left.left.right = new Node(5);
head.right.left.right = new Node(14);
head.right.left.right.left = new Node(11);
head.right.left.right.right = new Node(15);
head.right.right = new Node(13);
head.right.right.left = new Node(20);
head.right.right.right = new Node(16);
printTree(head);
Node bst = biggestSubBST(head);
printTree(bst);
}
}