/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
class Solution {
private HashMap<Integer,Integer> map = new HashMap<>();
public int deepestLeavesSum(TreeNode root) {
Queue<TreeNode> queue = new LinkedList<>();
queue.add(root);
int cen = 1;
while(!queue.isEmpty()){
Queue<TreeNode> ruuningqueue = new LinkedList<>();
while(!queue.isEmpty()){
TreeNode polltreenode = queue.poll();
this.map.merge(cen, polltreenode.val, Integer::sum);
if(polltreenode.left !=null){
ruuningqueue.add(polltreenode.left);
}
if(polltreenode.right != null){
ruuningqueue.add(polltreenode.right);
}
}
cen+=1;
queue = ruuningqueue;
}
int maxkey = -1;
for(Integer key : this.map.keySet()){
maxkey = Math.max(key,maxkey);
}
return this.map.get(maxkey);
}
}
leetcode双周赛的题:这道题需要求最深的一层的元素和。遇到二叉树的层次相关问题,第一反应就是想到用队列逐层次进行遍历。