17.判断子树

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