题解 | #牛群仰视图#

import java.util.*;

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

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param root TreeNode类 
     * @return int整型一维数组
     */
    public int[] bottomView (TreeNode root) {
        // write code here
        // 其实就是叶子节点
        if (root == null) {
            return new int[]{};
        }
        int i = getCount(root);
        System.out.print(i);
        int[] res = new int[i];
        i = 0;
        TreeNode cur = root;
        TreeNode mostRight = null;
        while (cur != null) {
            mostRight = cur.left;
            if (mostRight != null) {
                while (mostRight.right != null && mostRight.right != cur) {
                    mostRight = mostRight.right;
                }
                if(mostRight.right == null) {
                    // 第一次到达
                    // res[i++] = mostRight.val;
                    mostRight.right = cur;
                    cur = cur.left;
                    continue;
                } else {
                    // 第二次到达
                    if (mostRight.left == null) {
                        res[i++] = mostRight.val;
                    }
                    mostRight.right = null;
                }
            }
            cur = cur.right;
        }
        cur = root;
        while (cur.right != null) {
            cur = cur.right;
        }
        res[i++] = cur.val;
        return res;
    }
    //1, 2, 3, 4, #, #, 5}  4,5
    public int getCount(TreeNode root) {
        if (root == null) return 0;
        if (root.left == null && root.right == null) return 1;
        return getCount(root.left) + getCount(root.right);
    }
}