add solution 0002 [golang]

Author: lightfish-zhang

solution/0002.Add Two Numbers/Solution.go

@@ -0,0 +1,53 @@
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ *
+ * Report by leetcode.com
+ * Runtime: 12 ms, Memory Usage: 5 MB
+ */
+func addTwoNumbers(l1 *ListNode, l2 *ListNode) *ListNode {
+	head := &ListNode{}
+	currentNode1 := l1
+	currentNode2 := l2
+	currentHead := head
+	sum := 0
+	nextSum := 0
+
+	for true {
+		if currentNode1 != nil || currentNode2 != nil {
+			if currentNode1 == nil {
+				sum = nextSum + currentNode2.Val
+				nextSum = sum / 10
+				currentNode2 = currentNode2.Next
+			} else if currentNode2 == nil {
+				sum = nextSum + currentNode1.Val
+				nextSum = sum / 10
+				currentNode1 = currentNode1.Next
+			} else {
+				sum = nextSum + currentNode1.Val + currentNode2.Val
+				nextSum = sum / 10
+				currentNode1 = currentNode1.Next
+				currentNode2 = currentNode2.Next
+			}
+			currentHead.Val = sum % 10
+			// If there are elements present in the nodes then
+			// make a new node for future addition otherwise we
+			// will get unnecessary (0 --> <nil>) node in the end.
+			if currentNode1 != nil || currentNode2 != nil {
+				currentHead.Next = &ListNode{}
+				currentHead = currentHead.Next
+			} else if nextSum != 0 {
+				// If nextSum is not 0 this means that there was some carry value
+				// left in it which should be further.
+				currentHead.Next = &ListNode{nextSum, nil}
+			}
+		} else {
+			break
+		}
+	}
+
+	return head
+}