From b65db3b4f2bf6201c8eec03e5551f881b1c2818b Mon Sep 17 00:00:00 2001
From: Alec Goncharow <alec@goncharow.dev>
Date: Fri, 10 Jul 2026 12:32:02 -0400
Subject: words

---
 twosum/twosum.go | 112 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 112 insertions(+)
 create mode 100644 twosum/twosum.go

(limited to 'twosum/twosum.go')

diff --git a/twosum/twosum.go b/twosum/twosum.go
new file mode 100644
index 0000000..ca93104
--- /dev/null
+++ b/twosum/twosum.go
@@ -0,0 +1,112 @@
+package main
+
+import "fmt"
+
+type ListNode struct {
+	Val  int
+	Next *ListNode
+}
+
+func addTwoNumbers(l1 *ListNode, l2 *ListNode) *ListNode {
+	carry := 0
+	var output, co *ListNode
+	c1 := l1
+	c2 := l2
+	for {
+		if c1 != nil && c2 != nil {
+			sum := c1.Val + c2.Val + carry
+			carry = sum / 10
+			rem := sum % 10
+			c1.Val = rem
+			c2.Val = rem
+
+			if c1.Next == nil && c2.Next == nil {
+				if carry > 0 {
+					c1.Next = &ListNode{
+						Val: 1,
+					}
+					carry = 0
+				}
+			}
+
+			c1 = c1.Next
+			c2 = c2.Next
+			continue
+		}
+
+		if c1 != nil {
+			output = l1
+			co = c1
+			break
+		} else if c2 != nil {
+			output = l2
+			co = c2
+			break
+		} else {
+
+			output = l1
+			break
+		}
+	}
+
+	if co != nil {
+		for {
+			sum := co.Val + carry
+			carry = sum / 10
+			rem := sum % 10
+
+			co.Val = rem
+			if co.Next == nil {
+				if carry > 0 {
+					co.Next = &ListNode{
+						Val: 1,
+					}
+				}
+				break
+			}
+			co = co.Next
+		}
+	}
+
+	return output
+}
+
+func makeList(list []int) *ListNode {
+	output := &ListNode{
+		Val:  list[0],
+		Next: nil,
+	}
+	current := output
+	for _, n := range list[1:] {
+		node := &ListNode{
+			Val: n,
+		}
+		current.Next = node
+		current = node
+	}
+
+	return output
+}
+
+func printList(node *ListNode) {
+	for {
+		if node == nil {
+			break
+		}
+
+		fmt.Print(node.Val)
+		node = node.Next
+	}
+	fmt.Println()
+}
+
+func main() {
+	// Input: l1 = [9,9,9,9,9,9,9], l2 = [9,9,9,9]
+	// Output: [8,9,9,9,0,0,0,1]
+	l1 := makeList([]int{9, 9, 9, 9, 9, 9, 9})
+	l2 := makeList([]int{9, 9, 9, 9})
+	printList(l1)
+	printList(l2)
+
+	printList(addTwoNumbers(l1, l2))
+}
-- 
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