Merge pull request #780 from openset/develop

A: Merge k Sorted Lists

Author: Shuo

problems/merge-k-sorted-lists/README.md

@@ -26,9 +26,9 @@
 </pre>
 
 ### Related Topics
-  [[Heap](../../tag/heap/README.md)]
   [[Linked List](../../tag/linked-list/README.md)]
   [[Divide and Conquer](../../tag/divide-and-conquer/README.md)]
+  [[Heap](../../tag/heap/README.md)]
 
 ### Similar Questions
   1. [Merge Two Sorted Lists](../merge-two-sorted-lists) (Easy)

problems/merge-k-sorted-lists/merge_k_sorted_lists.go

@@ -1 +1,34 @@
 package problem23
+
+import "github.com/openset/leetcode/internal/kit"
+
+// ListNode - Definition for singly-linked list.
+type ListNode = kit.ListNode
+
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func mergeKLists(lists []*ListNode) *ListNode {
+	var ans *ListNode
+	for _, l := range lists {
+		ans = mergeTwoLists(ans, l)
+	}
+	return ans
+}
+
+func mergeTwoLists(l1 *ListNode, l2 *ListNode) *ListNode {
+	if l1 == nil {
+		return l2
+	} else if l2 == nil {
+		return l1
+	}
+	if l1.Val > l2.Val {
+		l1, l2 = l2, l1
+	}
+	l1.Next = mergeTwoLists(l1.Next, l2)
+	return l1
+}

problems/merge-k-sorted-lists/merge_k_sorted_lists_test.go

@@ -1 +1,51 @@
 package problem23
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/openset/leetcode/internal/kit"
+)
+
+type testType struct {
+	in   [][]int
+	want []int
+}
+
+func TestMergeKLists(t *testing.T) {
+	tests := [...]testType{
+		{
+			in: [][]int{
+				{1, 4, 5},
+				{1, 3, 4},
+				{2, 6},
+			},
+			want: []int{1, 1, 2, 3, 4, 4, 5, 6},
+		},
+		{
+			in: [][]int{
+				{2},
+				{},
+				{-1},
+			},
+			want: []int{-1, 2},
+		},
+		{
+			in: [][]int{
+				{},
+				{},
+			},
+			want: nil,
+		},
+	}
+	for _, tt := range tests {
+		lists := make([]*ListNode, len(tt.in))
+		for i, v := range tt.in {
+			lists[i] = kit.SliceInt2ListNode(v)
+		}
+		got := kit.ListNode2SliceInt(mergeKLists(lists))
+		if !reflect.DeepEqual(got, tt.want) {
+			t.Fatalf("in: %v, got: %v, want: %v", tt.in, got, tt.want)
+		}
+	}
+}