add new solutions

solutions/0/q1/solution.go

@@ -0,0 +1,22 @@
+package q1
+
+import "slices"
+
+func twoSum(nums []int, target int) []int {
+	pointers := make([]int, len(nums))
+	for i := range pointers {
+		pointers[i] = i
+	}
+
+	slices.SortFunc(pointers, func(a, b int) int { return nums[a] - nums[b] })
+	for l, r := 0, len(pointers)-1; l < r; l++ {
+		for ; l < r-1 && nums[pointers[l]]+nums[pointers[r]] > target; r-- {
+		}
+		if nums[pointers[l]]+nums[pointers[r]] == target {
+			return []int{pointers[l], pointers[r]}
+		}
+	}
+	return nil
+}
+
+var _ = twoSum

solutions/0/q13/solution.go

@@ -0,0 +1,37 @@
+package q13
+
+func lookup(b byte) int {
+	switch b {
+	case 'I':
+		return 1
+	case 'V':
+		return 5
+	case 'X':
+		return 10
+	case 'L':
+		return 50
+	case 'C':
+		return 100
+	case 'D':
+		return 500
+	case 'M':
+		return 1000
+	}
+	return 0
+}
+
+func romanToInt(s string) int {
+	num := 0
+	prev := 0
+	for i := range len(s) {
+		cur := lookup(s[i])
+		num += cur
+		if prev < cur {
+			num -= prev + prev
+		}
+		prev = cur
+	}
+	return num
+}
+
+var _ = romanToInt

solutions/0/q21/solution.go

@@ -0,0 +1,36 @@
+package q21
+
+type ListNode struct {
+	Val  int
+	Next *ListNode
+}
+
+func mergeTwoLists(list1 *ListNode, list2 *ListNode) *ListNode {
+	root := &ListNode{}
+	cur := root
+
+	for {
+		if list1 == nil && list2 == nil {
+			return root.Next
+		}
+		if list1 == nil {
+			cur.Next = list2
+			return root.Next
+		} else if list2 == nil {
+			cur.Next = list1
+			return root.Next
+		} else if list1.Val < list2.Val {
+			cur.Next = list1
+			cur = cur.Next
+			list1 = list1.Next
+			cur.Next = nil
+		} else {
+			cur.Next = list2
+			cur = cur.Next
+			list2 = list2.Next
+			cur.Next = nil
+		}
+	}
+}
+
+var _ = mergeTwoLists