Add Soulution.go for 0023.Merge k Sorted Lists

Author: Yeqi Tao

solution/0023.Merge k Sorted Lists/Solution.go

@@ -0,0 +1,53 @@
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+ func mergeKLists(lists []*ListNode) *ListNode {
+	if len(lists) == 0 {
+		return nil
+	}
+	for len(lists) != 1 {
+		newLists := make([]*ListNode, 0)
+		for i:=0; i<len(lists); i ++ {
+			if i < len(lists) - 1 {
+				nl := merge2List(lists[i], lists[i+1])
+				newLists = append(newLists, nl)
+				i++
+			} else if i == len(lists) - 1 && len(lists)%2 == 1 {
+				newLists = append(newLists, lists[i])
+			}
+		}
+		lists = newLists
+	}
+	return lists[0]
+}
+
+func merge2List(l1, l2 *ListNode) *ListNode {
+	p := &ListNode{}
+    h := p
+	for l1 != nil || l2 != nil {
+		if l1 == nil && l2 != nil {
+			p.Next = l2
+            p = p.Next
+			l2 = l2.Next
+		} else if l1 != nil && l2 == nil {
+			p.Next = l1
+            p = p.Next
+			l1 = l1.Next
+		} else {
+			if l1.Val < l2.Val {
+				p.Next = l1
+                p = p.Next
+				l1 = l1.Next
+			} else {
+				p.Next = l2
+                p = p.Next
+				l2 = l2.Next
+			}
+		}
+	}
+	return h.Next
+}