網易實習生筆試編程題 二叉樹

有一棵二叉樹，樹上每個點標有權值，權值各不相同，請設計一個算法算出權值最大的葉節點到權值最小的葉節點的距離。二叉樹每條邊的距離爲1，一個節點經過多少條邊到達另一個節點爲這兩個節點之間的距離。

給定二叉樹的根節點root，請返回所求距離。

import java.util.*;

/*
public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;
    public TreeNode(int val) {
        this.val = val;
    }
}*/

<span style="color: rgb(0, 188, 155); font-family: Monaco, Menlo, Consolas, 'Courier New', monospace; font-size: 13px; line-height: 18px; white-space: nowrap;">//典型的二進制編碼題，算出葉子節點二進制編碼，再比編碼，計算後綴長度和</span>
public class Tree {
    private StringBuilder maxCode = new StringBuilder();
    private StringBuilder minCode = new StringBuilder();
    private int min = Integer.MAX_VALUE;
    private int max = Integer.MIN_VALUE;
    public void preOrder(TreeNode root, char c, StringBuilder code) {
        if(root != null) {
            code.append(c);
            if(root.left == null && root.right == null) {
                if(min > root.val) {
                    min = root.val;
                    minCode = code;
                }
                if(max < root.val) {
                    max = root.val;
                    maxCode = code;
                }
            }
            preOrder(root.left, '0', new StringBuilder(code));
        	preOrder(root.right, '1', new StringBuilder(code));
        }
        
    }
    public int getDis(TreeNode root) {
        preOrder(root, '0', new StringBuilder());
        int index = 0;
        for(index = 0; index < (maxCode.length() > minCode.length() ? maxCode.length() : minCode.length()); index++) {
			if(maxCode.charAt(index) != minCode.charAt(index)) {
                break;
            }
        }
        return (maxCode.substring(index).length() + minCode.substring(index).length());
    }
}