138. Copy List with Random Pointer && upgrade to go1.23

Author: legolas.zhan

.gitignore

@@ -2,4 +2,5 @@ result
 leetcode.db
 .vscode/
 
-vendor/*
+vendor/*
+.DS_Store

go.mod

@@ -1,6 +1,6 @@
 module github.com/TTWShell/algorithms
 
-go 1.19
+go 1.23
 
 require github.com/stretchr/testify v1.7.0
 

leetcode/linked-list/copyRandomList.go

@@ -0,0 +1,48 @@
+/* https://leetcode.com/problems/copy-list-with-random-pointer/?envType=study-plan-v2&envId=top-interview-150
+ */
+
+package lll
+
+type Node struct {
+	Val    int
+	Next   *Node
+	Random *Node
+}
+
+func copyRandomList(head *Node) *Node {
+	if head == nil {
+		return nil
+	}
+
+	// Step 1: Insert copy nodes into original list
+	cur := head
+	for cur != nil {
+		newNode := &Node{Val: cur.Val, Next: cur.Next}
+		cur.Next = newNode
+		cur = newNode.Next
+	}
+
+	// Step 2: Assign random pointers for copied nodes
+	cur = head
+	for cur != nil {
+		if cur.Random != nil {
+			cur.Next.Random = cur.Random.Next
+		}
+		cur = cur.Next.Next
+	}
+
+	// Step 3: Separate original and copied lists
+	oldList := head
+	newList := head.Next
+	newHead := newList
+	for oldList != nil {
+		oldList.Next = oldList.Next.Next
+		if newList.Next != nil {
+			newList.Next = newList.Next.Next
+		}
+		oldList = oldList.Next
+		newList = newList.Next
+	}
+
+	return newHead
+}

leetcode/linked-list/copyRandomList_test.go

@@ -0,0 +1,83 @@
+package lll
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCopyRandomList(t *testing.T) {
+	// Helper function to build linked list from input
+	buildList := func(input [][]interface{}) *Node {
+		if len(input) == 0 {
+			return nil
+		}
+		nodes := make([]*Node, len(input))
+		for i, val := range input {
+			nodes[i] = &Node{Val: val[0].(int)}
+		}
+		for i, val := range input {
+			if i < len(input)-1 {
+				nodes[i].Next = nodes[i+1]
+			}
+			if val[1] != nil {
+				nodes[i].Random = nodes[val[1].(int)]
+			}
+		}
+		return nodes[0]
+	}
+
+	// Helper function to convert list to [][]interface{} for comparison
+	convertList := func(head *Node) [][]interface{} {
+		var result [][]interface{}
+		indexMap := make(map[*Node]int)
+		cur := head
+		index := 0
+		for cur != nil {
+			indexMap[cur] = index
+			cur = cur.Next
+			index++
+		}
+		cur = head
+		for cur != nil {
+			if cur.Random != nil {
+				result = append(result, []interface{}{cur.Val, indexMap[cur.Random]})
+			} else {
+				result = append(result, []interface{}{cur.Val, nil})
+			}
+
+			cur = cur.Next
+		}
+		return result
+	}
+
+	tests := []struct {
+		name     string
+		input    [][]interface{}
+		expected [][]interface{}
+	}{
+		{
+			name:     "Example 1",
+			input:    [][]interface{}{{7, nil}, {13, 0}, {11, 4}, {10, 2}, {1, 0}},
+			expected: [][]interface{}{{7, nil}, {13, 0}, {11, 4}, {10, 2}, {1, 0}},
+		},
+		{
+			name:     "Example 2",
+			input:    [][]interface{}{{1, 1}, {2, 1}},
+			expected: [][]interface{}{{1, 1}, {2, 1}},
+		},
+		{
+			name:     "Example 3",
+			input:    [][]interface{}{{3, nil}, {3, 0}, {3, nil}},
+			expected: [][]interface{}{{3, nil}, {3, 0}, {3, nil}},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			head := buildList(tt.input)
+			copiedList := copyRandomList(head)
+			assert.Equal(t, tt.expected, convertList(copiedList))
+		})
+	}
+}