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0515.在每个树行中找最大值
描述
您需要在二叉树的每一行中找到最大的值。
实例
输入:
1
/ \
3 2
/ \ \
5 3 9
输出: [1, 3, 9]
题解
逐层遍历,对每一层找到最大值
public ArrayList<TreeNode> getNextLayNodes(ArrayList<TreeNode> layList1){
ArrayList<TreeNode> layList2 = new ArrayList<>();
for(TreeNode node:layList1){
if (node.left != null)
layList2.add(node.left);
if (node.right != null)
layList2.add(node.right);
}
return layList2;
}
public List<Integer> largestValues(TreeNode root) {
List<Integer> result = new ArrayList<>();
if (root == null)
return result;
ArrayList<TreeNode> layList1;
ArrayList<TreeNode> layList2;
layList1 = new ArrayList<>();
layList1.add(root);
while (!layList1.isEmpty()){
layList2 = getNextLayNodes(layList1);
int max = Integer.MIN_VALUE;
for (TreeNode node:layList1)
max = max > node.val ? max : node.val;
result.add(max);
layList1 = layList2;
}
return result;
}