90 lines
2.2 KiB
Java
90 lines
2.2 KiB
Java
//给定一棵二叉树，返回所有重复的子树。对于同一类的重复子树，你只需要返回其中任意一棵的根结点即可。
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//
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// 两棵树重复是指它们具有相同的结构以及相同的结点值。
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//
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// 示例 1：
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//
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// 1
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// / \
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// 2 3
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// / / \
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// 4 2 4
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// /
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// 4
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//
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//
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// 下面是两个重复的子树：
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//
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// 2
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// /
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// 4
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//
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//
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// 和
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//
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// 4
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//
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//
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// 因此，你需要以列表的形式返回上述重复子树的根结点。
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// Related Topics 树 深度优先搜索 广度优先搜索 二叉树 👍 303 👎 0
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package leetcode.editor.cn;
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import com.code.leet.entiy.TreeNode;
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import java.util.ArrayList;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Map;
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//652:寻找重复的子树
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class FindDuplicateSubtrees {
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public static void main(String[] args) {
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//测试代码
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Solution solution = new FindDuplicateSubtrees().new Solution();
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}
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//力扣代码
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//leetcode submit region begin(Prohibit modification and deletion)
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/**
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* Definition for a binary tree node.
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* public class TreeNode {
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* int val;
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* TreeNode left;
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* TreeNode right;
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* TreeNode() {}
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* TreeNode(int val) { this.val = val; }
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* TreeNode(int val, TreeNode left, TreeNode right) {
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* this.val = val;
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* this.left = left;
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* this.right = right;
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* }
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* }
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*/
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class Solution {
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Map<String, Integer> count;
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List<TreeNode> ans;
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public List<TreeNode> findDuplicateSubtrees(TreeNode root) {
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count = new HashMap();
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ans = new ArrayList();
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collect(root);
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return ans;
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}
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public String collect(TreeNode node) {
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if (node == null) {
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return "#";
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}
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String serial = node.val + "," + collect(node.left) + "," + collect(node.right);
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count.put(serial, count.getOrDefault(serial, 0) + 1);
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if (count.get(serial) == 2) {
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ans.add(node);
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}
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return serial;
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}
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}
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//leetcode submit region end(Prohibit modification and deletion)
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} |