题解 | 判断是不是完全二叉树
判断是不是完全二叉树
https://www.nowcoder.com/practice/8daa4dff9e36409abba2adbe413d6fae
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 bool布尔型
*/
public boolean isCompleteTree (TreeNode root) {
if (root == null) {
return true;
}
List<Integer> list = new ArrayList<>();
height(root, list, 0);
Set<Integer> set = new HashSet<>();
set.add(list.get(0));
for (int i = 1; i < list.size(); i++) {
if (list.get(i - 1) < list.get(i)) {
return false;
}
set.add(list.get(i - 1));
}
if (set.size() > 2) {
return false;
}
return true;
}
static public void height(TreeNode root, List<Integer> list, int height) {
if (root == null) {
list.add(height);
return;
}
height(root.left, list, height + 1);
height(root.right, list, height + 1);
}
}
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