diff --git a/solutions/0/q1/solution.go b/solutions/0/q1/solution.go
new file mode 100644
index 0000000..72db61f
--- /dev/null
+++ b/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
diff --git a/solutions/0/q13/solution.go b/solutions/0/q13/solution.go
new file mode 100644
index 0000000..b281763
--- /dev/null
+++ b/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
diff --git a/solutions/0/q21/solution.go b/solutions/0/q21/solution.go
new file mode 100644
index 0000000..79cb325
--- /dev/null
+++ b/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
diff --git a/solutions/1/q100/solution.go b/solutions/1/q100/solution.go
new file mode 100644
index 0000000..255748e
--- /dev/null
+++ b/solutions/1/q100/solution.go
@@ -0,0 +1,27 @@
+package q100
+
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+func traverse(p, q *TreeNode) bool {
+	if p == nil && q == nil {
+		return true
+	}
+	if p == nil || q == nil {
+		return false
+	}
+	if p.Val != q.Val {
+		return false
+	}
+	return traverse(p.Left, q.Left) &&
+		traverse(p.Right, q.Right)
+}
+
+func isSameTree(p *TreeNode, q *TreeNode) bool {
+	return traverse(p, q)
+}
+
+var _ = isSameTree
diff --git a/solutions/1/q101/solution.go b/solutions/1/q101/solution.go
new file mode 100644
index 0000000..062ca32
--- /dev/null
+++ b/solutions/1/q101/solution.go
@@ -0,0 +1,27 @@
+package q101
+
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+func traverse(left, right *TreeNode) bool {
+	if left == nil && right == nil {
+		return true
+	}
+	if left == nil || right == nil {
+		return false
+	}
+	if left.Val != right.Val {
+		return false
+	}
+	return traverse(left.Left, right.Right) &&
+		traverse(left.Right, right.Left)
+}
+
+func isSymmetric(root *TreeNode) bool {
+	return traverse(root.Left, root.Right)
+}
+
+var _ = isSymmetric
diff --git a/solutions/1/q112/solution.go b/solutions/1/q112/solution.go
new file mode 100644
index 0000000..5571d73
--- /dev/null
+++ b/solutions/1/q112/solution.go
@@ -0,0 +1,26 @@
+package q112
+
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+func traverse(node *TreeNode, tgtSum, curSum int) bool {
+	if node == nil {
+		return false
+	}
+
+	sum := curSum + node.Val
+	if node.Left == nil && node.Right == nil && sum == tgtSum {
+		return true
+	}
+	return traverse(node.Left, tgtSum, sum) ||
+		traverse(node.Right, tgtSum, sum)
+}
+
+func hasPathSum(root *TreeNode, targetSum int) bool {
+	return traverse(root, targetSum, 0)
+}
+
+var _ = hasPathSum
diff --git a/solutions/13/q1351/solution.go b/solutions/13/q1351/solution.go
new file mode 100644
index 0000000..823d8c3
--- /dev/null
+++ b/solutions/13/q1351/solution.go
@@ -0,0 +1,17 @@
+package q1351
+
+func countNegatives(grid [][]int) int {
+	w := len(grid[0])
+	count := 0
+
+	countRow := 0
+	for r := range grid {
+		for countRow < w && (grid[r][w-countRow-1] < 0) {
+			countRow++
+		}
+		count += countRow
+	}
+	return count
+}
+
+var _ = countNegatives
diff --git a/solutions/2/q205/solution.go b/solutions/2/q205/solution.go
new file mode 100644
index 0000000..aea8514
--- /dev/null
+++ b/solutions/2/q205/solution.go
@@ -0,0 +1,26 @@
+package q205
+
+func isIsomorphic(s string, t string) bool {
+	if len(s) != len(t) {
+		return false
+	}
+
+	ab := make(map[byte]byte, 256)
+	ba := make(map[byte]byte, 256)
+	for i := range len(s) {
+		if b, ok := ab[s[i]]; ok {
+			if t[i] != b {
+				return false
+			}
+		} else {
+			if _, ok := ba[t[i]]; ok {
+				return false
+			}
+			ab[s[i]] = t[i]
+			ba[t[i]] = s[i]
+		}
+	}
+	return true
+}
+
+var _ = isIsomorphic
diff --git a/solutions/2/q219/solution.go b/solutions/2/q219/solution.go
new file mode 100644
index 0000000..86b96d8
--- /dev/null
+++ b/solutions/2/q219/solution.go
@@ -0,0 +1,18 @@
+package q219
+
+func containsNearbyDuplicate(nums []int, k int) bool {
+	seen := make(map[int]struct{}, k)
+
+	for i, num := range nums {
+		if _, ok := seen[num]; ok {
+			return true
+		}
+		seen[num] = struct{}{}
+		if i >= k {
+			delete(seen, nums[i-k])
+		}
+	}
+	return false
+}
+
+var _ = containsNearbyDuplicate
diff --git a/solutions/2/q290/solution.go b/solutions/2/q290/solution.go
new file mode 100644
index 0000000..8f29154
--- /dev/null
+++ b/solutions/2/q290/solution.go
@@ -0,0 +1,30 @@
+package q290
+
+import "strings"
+
+func wordPattern(pattern string, s string) bool {
+	index := map[byte]string{}
+	invIndex := map[string]struct{}{}
+
+	fields := strings.Fields(s)
+	if len(fields) != len(pattern) {
+		return false
+	}
+
+	for i, word := range fields {
+		if w, ok := index[pattern[i]]; ok {
+			if w != word {
+				return false
+			}
+		} else {
+			if _, ok := invIndex[word]; ok {
+				return false
+			}
+			index[pattern[i]] = word
+			invIndex[word] = struct{}{}
+		}
+	}
+	return true
+}
+
+var _ = wordPattern
diff --git a/solutions/24/q2402/solution.go b/solutions/24/q2402/solution.go
new file mode 100644
index 0000000..c95acc6
--- /dev/null
+++ b/solutions/24/q2402/solution.go
@@ -0,0 +1,77 @@
+package q2402
+
+import (
+	"container/heap"
+	"slices"
+)
+
+type Room struct {
+	id           int
+	meetingStart int
+	meetingEnd   int
+}
+
+type Rooms []Room
+
+func (r *Rooms) Len() int          { return len(*r) }
+func (r *Rooms) Push(x any)        { (*r) = append((*r), x.(Room)) }
+func (r *Rooms) Swap(i int, j int) { (*r)[i], (*r)[j] = (*r)[j], (*r)[i] }
+
+func (r *Rooms) Less(i int, j int) bool {
+	if (*r)[i].meetingEnd == (*r)[j].meetingEnd {
+		return (*r)[i].id < (*r)[j].id
+	}
+	return (*r)[i].meetingEnd < (*r)[j].meetingEnd
+}
+
+func (r *Rooms) Pop() any {
+	last := len(*r) - 1
+	ret := (*r)[last]
+	*r = (*r)[:last]
+	return ret
+}
+
+func mostBooked(n int, meetings [][]int) int {
+	timesBooked := make([]int, n)
+	empty := make(Rooms, n)
+	for i := range empty {
+		empty[i] = Room{id: i}
+	}
+	inUse := make(Rooms, 0, n)
+
+	slices.SortFunc(meetings, func(a, b []int) int { return a[0] - b[0] })
+	for i := range meetings {
+		start, end := meetings[i][0], meetings[i][1]
+		for len(inUse) > 0 && inUse[0].meetingEnd <= start {
+			heap.Push(&empty, Room{id: inUse[0].id})
+			heap.Pop(&inUse)
+		}
+
+		if len(empty) > 0 {
+			id := empty[0].id
+			timesBooked[id]++
+			heap.Push(&inUse, Room{
+				id:           id,
+				meetingStart: start,
+				meetingEnd:   end,
+			})
+			heap.Pop(&empty)
+		} else {
+			room := &inUse[0]
+			timesBooked[room.id]++
+			room.meetingStart, room.meetingEnd = room.meetingEnd, end-start+room.meetingEnd
+			heap.Fix(&inUse, 0)
+		}
+	}
+
+	mb, mbIdx := timesBooked[0], 0
+	for i := 1; i < len(timesBooked); i++ {
+		if timesBooked[i] > mb {
+			mb, mbIdx = timesBooked[i], i
+		}
+	}
+	return mbIdx
+}
+
+var _ heap.Interface = &Rooms{}
+var _ = mostBooked