题目:一棵二叉树,求最大通路长度(即最大左右子树高度之和)
参考答案:
该题与leetcode第104题同题型,定义TreeNode结构如下:
class TreeNode {
int val;
TreeNode left;
TreeNode right;
public TreeNode(int val) {
this.val = val;
}
}
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解法一(递归求解)
class Solution {
public int maxHeight(TreeNode root) {
if (root == null) {
return 0;
}
return maxChildHeight(root.left) + maxChildHeight(root.right);
}
public int maxChildHeight(TreeNode root) {
if (root == null) {
return 0;
}
int leftHeight = maxChildHeight(root.left);
int rightHeight = maxChildHeight(root.right);
return Math.max(leftHeight, rightHeight) + 1;
}
}
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解法二(迭代求解)
public class Solution {
public int maxHeight(TreeNode root) {
if (root == null) {
return 0;
}
return maxChildHeight(root.left) + maxChildHeight(root.right);
}
public int maxChildHeight(TreeNode root) {
int height = 0;
Queue<TreeNode> queue = new LinkedList<>();
queue.add(root);
while (!queue.isEmpty()) {
int size = queue.size();
for (int i = 0; i < size; i++) {
TreeNode node = queue.poll();
height++;
if (node.left != null) {
queue.add(node.left);
}
if (node.right != null) {
queue.add(node.right);
}
}
}
return height;
}
}
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