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You need to find the largest value in each row of a binary tree.
Example:
Input: 1 / \ 3 2 / \ \ 5 3 9 Output: [1, 3, 9]
思路:BFS,用queue来收集每行的node,取最大值即可;
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
class Solution {
public List<Integer> largestValues(TreeNode root) {
List<Integer> list = new ArrayList<Integer>();
if(root == null) return list;
LinkedList<TreeNode> queue = new LinkedList<TreeNode>();
queue.add(root);
while(!queue.isEmpty()){
int size = queue.size();
int curMax = Integer.MIN_VALUE;
while(size>0){
TreeNode node = queue.poll();
size--;
curMax = Math.max(curMax,node.val);
if(node.left!=null){
queue.add(node.left);
}
if(node.right!=null){
queue.add(node.right);
}
}
list.add(curMax);
}
return list;
}
}