solve 2: add two numbers

Author: andavid

vscode/2.add-two-numbers.java

@@ -0,0 +1,70 @@
+/*
+ * @lc app=leetcode id=2 lang=java
+ *
+ * [2] Add Two Numbers
+ *
+ * https://leetcode.com/problems/add-two-numbers/description/
+ *
+ * algorithms
+ * Medium (30.61%)
+ * Total Accepted:    801.6K
+ * Total Submissions: 2.6M
+ * Testcase Example:  '[2,4,3]\n[5,6,4]'
+ *
+ * You are given two non-empty linked lists representing two non-negative
+ * integers. 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.
+ * 
+ * You may assume the two numbers do not contain any leading zero, except the
+ * number 0 itself.
+ * 
+ * Example:
+ * 
+ * 
+ * Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
+ * Output: 7 -> 0 -> 8
+ * Explanation: 342 + 465 = 807.
+ * 
+ * 
+ */
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode(int x) { val = x; }
+ * }
+ */
+class Solution {
+  public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
+    int sum = 0;
+    ListNode p1 = l1;
+    ListNode p2 = l2;
+    ListNode dummy = new ListNode(-1);
+    ListNode p = dummy;
+
+    while (p1 != null || p2 != null) {
+      sum /= 10;
+
+      if (p1 != null) {
+        sum += p1.val;
+        p1 = p1.next;
+      }
+
+      if (p2 != null) {
+        sum += p2.val;
+        p2 = p2.next;
+      }
+
+      p.next = new ListNode(sum % 10);
+      p = p.next;
+    }
+
+    if (sum / 10 == 1) {
+      p.next = new ListNode(1);
+    }
+
+    return dummy.next;
+  }
+}
+