LeetCode 951 Flip Equivalent Binary Trees

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题目描述

For a binary tree T, we can define a flip operation as follows: choose any node, and swap the left and right child subtrees.

A binary tree X is flip equivalent to a binary tree Y if and only if we can make X equal to Y after some number of flip operations.

Write a function that determines whether two binary trees are flip equivalent. The trees are given by root nodes root1 and root2.

Example 1:

Input: root1 = [1,2,3,4,5,6,null,null,null,7,8], root2 = [1,3,2,null,6,4,5,null,null,null,null,8,7]
Output: true
Explanation: We flipped at nodes with values 1, 3, and 5.
Flipped Trees Diagram

Note:

Each tree will have at most 100 nodes.
Each value in each tree will be a unique integer in the range [0, 99].

代码

public boolean flipEquiv(TreeNode root1, TreeNode root2) {
    if (root1 == null && root2 == null) return true;
    if (root1 == null || root2 == null) return false;
    if (root1.val != root2.val) {
        return false;
    }
    return (flipEquiv(root1.left, root2.left) && flipEquiv(root1.right, root2.right)) ||
            (flipEquiv(root1.left, root2.right) && flipEquiv(root1.right, root2.left));
}