题解 | #树的子结构#

/**
public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;

    }

}
*/
public class Solution {
    public boolean HasSubtree(TreeNode root1, TreeNode root2) {
        if (root1 == null || root2 == null) return false;
        if (sameTree(root1, root2)) {
            return true;
        } else {
            return HasSubtree(root1.left, root2) || HasSubtree(root1.right, root2);
        }
    }

    private boolean sameTree(TreeNode root1, TreeNode root2) {
        if (root2 == null) return true;
        if (root1 != null && root2 != null) {
            if (root1.val == root2.val) {
                return sameTree(root1.left, root2.left) && sameTree(root1.right, root2.right);
            } else {
                return false;
            }
        }
        return false;
    }
}

算法思想：递归判断根节点+递归判断左右子树