剑指offer 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;
        return hasSubtree(root1,root2)||hasSubtree(root1.left,root2)||hasSubtree(root1.right,root2);
    }
    private boolean hasSubtree(TreeNode root1,TreeNode root2){
        if(root2==null)
            return true;
        if(root1==null)
            return false;
        if(root1.val==root2.val)
            return hasSubtree(root1.left,root2.left)&&hasSubtree(root1.right,root2.right);
        else{
            return hasSubtree(root1.left,root2)||hasSubtree(root1.right,root2);
        }
    }
}