Find Largest Value in Each Tree Row
阿新 • • 發佈:2019-01-07
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來收集每行的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; } }