package com.binaryTree;

import org.omg.CORBA.MARSHAL;

import java.util.HashMap;
import java.util.LinkedList;
import java.util.Map;
import java.util.Queue;

// 求二叉树最宽的层有多少个节点(即二叉树的最大宽度)
public class TreeMaxWidth {
    public static class Node {
        public int value;
        public Node left;
        public Node right;

        public Node(int data) {
            this.value = data;
        }
    }
    public static int maxWidth1(Node head){
        if (head == null){
            return 0;
        }
        Node curEnd = head; // 记录当前层的最后节点
        Node nextEnd = null;  // 记录下一层的最后节点
        int count = 0; // count记录当前层的节点个数(宽度)，因为由前面if判断知道，head不为null,故当前层的节点数为1
        int max = 0;  // 最后返回的最大宽度
        Queue<Node> queue = new LinkedList<>();
        queue.add(head);
        while (!queue.isEmpty()){
            Node cur = queue.poll();
            count++;  // 每从queue中poll节点但 cur!=curEnd(没遍历当前层的最后节点时)，当前层的节点数count+1
            if (cur.left != null){
                queue.add(cur.left);
                nextEnd = cur.left;
            }
            if (cur.right != null){
                queue.add(cur.right);
                nextEnd = cur.right;
            }

            if (cur == curEnd){
                max = Math.max(max,count);
                curEnd = nextEnd;
                count = 0;
            }
        }
        return max;
    }

    public static int maxWidth2(Node head){
        if (head == null){
            return 0;
        }
        Queue<Node> queue = new LinkedList<>();
        queue.add(head);
        int curLevel = 1; // 当前统计宽度的层数
        Map<Node,Integer> map = new HashMap<>();
        map.put(head,1);

        int count = 0;
        int max = 0;
        while (!queue.isEmpty()){
            Node cur = queue.poll();
            int nodeLevel = map.get(cur); // cur节点所在层数
            if (cur.left != null){
                map.put(cur.left,nodeLevel+1);
                queue.add(cur.left);
            }
            if (cur.right != null){
                map.put(cur.right,nodeLevel+1);
                queue.add(cur.right);
            }
            if (curLevel == nodeLevel){ // 当前统计宽度的层数与cur节点所在层数相等，节点数count +1
                count++;
            }else {
                curLevel++;
                max = Math.max(max,count);
                count = 1;
            }
        }
        max = Math.max(max,count);
        return max;
    }

    // for test
    public static Node generateRandomBST(int maxLevel, int maxValue) {
        return generate(1, maxLevel, maxValue);
    }

    // for test
    //  level为当前创建节点的层数
    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 = 10;
        int maxValue = 100;
        int testTimes = 1000000;
        System.out.println("test start:");
        for (int i = 0; i < testTimes; i++) {
            Node head = generateRandomBST(maxLevel, maxValue);
            if (maxWidth1(head) != maxWidth2(head)) {
                System.out.println("Oops!");
            }
        }
        System.out.println("finish!");
    }

}