same tree

题目：

Given two binary trees, write a function to check if they are equal or not.

Two binary trees are considered equal if they are structurally identical and the nodes have the same value.

public class SameTree {

	boolean isDiff;
	public boolean isSameTree(TreeNode p, TreeNode q) {
		if(p == null && q == null){
			return true;
		}
		isSame(p, q);
		return !isDiff;
    }
	private void isSame(TreeNode p, TreeNode q){
		if(isDiff){
			return;
		}
		if(p == null && q == null){
			return;
		}else if((p == null && q != null) || (p != null && q == null)){
			isDiff = true;
		}else{
			if(p.val == q.val){
				isSame(p.left, q.left);
				isSame(p.right, q.right);
			}else{
				isDiff = true;
			}
		}
	}
	public static void main(String[] args) {
		

	}

}