树的子结构

Question

这里对树是否是子结构的判断比较经典

/**
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 (root2 == null || root1 == null) return false;
        boolean result = false;
        if (root1.val == root2.val){
            result = check(root1,root2);
        }
        if (!result){
            result = HasSubtree(root1.left,root2);
        }
        if (!result){
            result = HasSubtree(root1.right,root2);
        }
        return result;
    }

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