题解 | #判断是不是完全二叉树#
判断是不是完全二叉树
http://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;
* }
* }
*/
//宽度优先遍历
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) {
// write code here
if(root == null){
return true;
}
Queue<TreeNode> queue = new LinkedList<>();
queue.add(root);
boolean isNull = false;
while(!queue.isEmpty()){
int size = queue.size();
for(int i = 0;i<size;i++){
isNull = true;
continue;
return false;
}
queue.offer(cur.left);
queue.offer(cur.right);
}
}
return true;
}
}
/*
* public class TreeNode {
* int val = 0;
* TreeNode left = null;
* TreeNode right = null;
* public TreeNode(int val) {
* this.val = val;
* }
* }
*/
//宽度优先遍历
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) {
// write code here
if(root == null){
return true;
}
Queue<TreeNode> queue = new LinkedList<>();
queue.add(root);
boolean isNull = false;
while(!queue.isEmpty()){
int size = queue.size();
for(int i = 0;i<size;i++){
TreeNode cur = queue.poll();
//出现空值，标志位变true;跳过以下步骤
if(cur == null){isNull = true;
continue;
}
//成立的条件是，前面出现空值之后，后面出现不为空的值
if(isNull){return false;
}
queue.offer(cur.left);
queue.offer(cur.right);
}
}
return true;
}
}