572. 另一棵树的子树

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class Solution {
    public boolean isSubtree(TreeNode root, TreeNode subRoot) {

        /**
         * 对于树的每个节点，都判断一下是否和子树是一个树（《100. 相同的树》）
         */
        if (subRoot == null){
            return true;
        }

        if (root == null){
            return false;
        }

        return isSubtree(root.left, subRoot) || isSubtree(root.right, subRoot) || isSameTree(root, subRoot);
    }

    public boolean isSameTree(TreeNode tree1, TreeNode tree2){

        if (tree1 == null || tree2 == null){
            return tree1 == tree2;
        }

        if (tree1.val == tree2.val) {
            return isSameTree(tree1.left, tree2.left) && isSameTree(tree1.right, tree2.right);
        }
        else {
            return false;
        }
    }
}

/**
 * 时间复杂度 O(n)
 * 空间复杂度 O(logn)
 */

https://leetcode-cn.com/problems/subtree-of-another-tree/