week 4

Author: bus710

merge-two-sorted-lists/bus710.go

@@ -0,0 +1,52 @@
+package hello
+
+type ListNode struct {
+	Val  int
+	Next *ListNode
+}
+
+func mergeTwoLists(list1 *ListNode, list2 *ListNode) *ListNode {
+	if list1 == nil && list2 == nil {
+		return nil
+	} else if list1 == nil {
+		return list2
+	} else if list2 == nil {
+		return list1
+	}
+
+	newList := &ListNode{}
+	cur := newList
+
+	for {
+		switch {
+		case list1.Val < list2.Val:
+			cur.Next = &ListNode{Val: list1.Val}
+			list1 = list1.Next
+		case list1.Val > list2.Val:
+			cur.Next = &ListNode{Val: list2.Val}
+			list2 = list2.Next
+		default:
+			cur.Next = &ListNode{Val: list1.Val}
+			list1 = list1.Next
+			cur = cur.Next
+			cur.Next = &ListNode{Val: list2.Val}
+			list2 = list2.Next
+		}
+		cur = cur.Next
+		if list1 == nil && list2 == nil && cur.Next == nil {
+			break
+		}
+
+		if list1 == nil {
+			cur.Next = list2
+			break
+		}
+		if list2 == nil {
+			cur.Next = list1
+			break
+		}
+
+	}
+
+	return newList.Next
+}