optimize 2

fishercoder1534 · fishercoder1534 · commit 1c6e93bbe4c7 · 2017-05-13T16:34:11.000-07:00
diff --git a/README.md b/README.md
@@ -424,7 +424,7 @@ Your ideas/fixes/algorithms are more than welcome!
 |5|[Longest Palindromic Substring](https://leetcode.com/problems/longest-palindromic-substring/)|[Solution](../master/src/main/java/com/stevesun/solutions/LongestPalindromicSubstring.java) | O(n^2) | O(1) | Medium|
 |4|[Median of Two Sorted Arrays](https://leetcode.com/problems/median-of-two-sorted-arrays/)|[Solution](../master/src/main/java/com/stevesun/solutions/MedianofTwoSortedArrays.java) | ? | ? | Hard | Divide and Conquer
 |3|[Longest Substring Without Repeating Characters](https://leetcode.com/problems/longest-substring-without-repeating-characters/)|[Solution](../master/src/main/java/com/stevesun/solutions/LongestSubstringWithoutRepeatingCharacters.java) | O(n) | O(1) | Medium | HashMap, Sliding Window
-|2|[Add Two Numbers](https://leetcode.com/problems/add-two-numbers/)|[Solution](../master/src/main/java/com/stevesun/solutions/AddTwoNumbers.java) | O(n) | O(1) | Medium | LinkedList
+|2|[Add Two Numbers](https://leetcode.com/problems/add-two-numbers/)|[Solution](../master/src/main/java/com/stevesun/solutions/_2.java) | O(max(m,n)) | O(1) | Medium | LinkedList
 |1|[Two Sum](https://leetcode.com/problems/two-sum/)|[Solution](../master/src/main/java/com/stevesun/solutions/_1.java)| O(n)/O(n^2)|O(1)/O(n) | Easy| HashMap
 
 ## Database
diff --git a/src/main/java/com/stevesun/solutions/AddTwoNumbers.java b/src/main/java/com/stevesun/solutions/AddTwoNumbers.java
diff --git a/src/main/java/com/stevesun/solutions/_2.java b/src/main/java/com/stevesun/solutions/_2.java
@@ -0,0 +1,35 @@
+package com.stevesun.solutions;
+
+import com.stevesun.common.classes.ListNode;
+import com.stevesun.common.utils.CommonUtils;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**2. Add Two Numbers
+You are given two linked lists representing two non-negative numbers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.
+
+Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
+Output: 7 -> 0 -> 8*/
+public class _2 {
+    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
+        ListNode result = new ListNode(0);
+        ListNode tmp = result;
+        int sum = 0;
+        while (l1 != null || l2 != null) {
+            sum /= 10;
+            if (l1 != null) {
+                sum += l1.val;
+                l1 = l1.next;
+            }
+            if (l2 != null) {
+                sum += l2.val;
+                l2 = l2.next;
+            }
+            tmp.next = new ListNode(sum%10);;
+            tmp = tmp.next;
+        }
+        if (sum/10 == 1) tmp.next = new ListNode(1);//this means there's a carry, so we add additional 1, e.g. [5] + [5] = [0, 1]
+        return result.val == 0 ? result.next : result;
+    }
+}
