100 Same Tree

First Attempt

/**

• Definition for a binary tree node.
• public class TreeNode {
• int val;
• TreeNode left;
• TreeNode right;
• TreeNode(int x) { val = x; }
• } */ public class Solution { public boolean isSameTree(TreeNode p, TreeNode q) {

   if (p == null && q == null) {
       return true;
   } else if (p == null || q == null) {
       return false;
   } else {
   // Here is a little tricky, I solve it for 3 times.
       if (p.val == q.val) {
           if (!isSameTree(p.left, q.left)) {
               return false;
           } 
           if (!isSameTree(p.right, q.right)) {
               return false;
           }
           return true;
       } else {
           return false;
       }
   }
  

  } }

Updated: precise one

/**

• Definition for a binary tree node.
• public class TreeNode {
• int val;
• TreeNode left;
• TreeNode right;
• TreeNode(int x) { val = x; }
• } */ public class Solution { public boolean isSameTree(TreeNode p, TreeNode q) {

   if (p == null && q == null) {
       return true;
   }
   if ((p == null || q == null) || (p.val != q.val)) {
       return false;
   }
   return isSameTree(p.left, q.left) && isSameTree(p.right, q.right);
  

  } }

Updated (12.19.15)

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public boolean isSameTree(TreeNode n1, TreeNode n2) {
        // forget return
        return helper(n1, n2);
    }
    private boolean helper(TreeNode n1, TreeNode n2) {
        if (n1 == null && n2 == null) {
            return true;
        }
        if (n1 == null || n2 == null) {
            return false;
        }
        return (n1.val == n2.val) && helper(n1.left, n2.left) && helper(n1.right, n2.right);
    }
}