diff --git a/solutions/1/q199/solution.go b/solutions/1/q199/solution.go
new file mode 100644
index 0000000..3ee35a9
--- /dev/null
+++ b/solutions/1/q199/solution.go
@@ -0,0 +1,37 @@
+package q199
+
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+func rightSideView(root *TreeNode) []int {
+	ret := []int{}
+
+	type qElem struct {
+		height int
+		node   *TreeNode
+	}
+
+	queue := []qElem{{0, root}}
+	var last *qElem
+	for ; len(queue) > 0; queue = queue[1:] {
+		cur := &queue[0]
+		if cur.node == nil {
+			continue
+		}
+		if last != nil && last.height < cur.height {
+			ret = append(ret, last.node.Val)
+		}
+		last = cur
+		queue = append(queue, qElem{cur.height + 1, cur.node.Left}, qElem{cur.height + 1, cur.node.Right})
+	}
+	if last != nil {
+		ret = append(ret, last.node.Val)
+	}
+
+	return ret
+}
+
+var _ = rightSideView
diff --git a/solutions/2/q200/solution.go b/solutions/2/q200/solution.go
new file mode 100644
index 0000000..9564d9a
--- /dev/null
+++ b/solutions/2/q200/solution.go
@@ -0,0 +1,31 @@
+package q200
+
+const (
+	VISITED byte = '.'
+	LAND    byte = '1'
+)
+
+func traverse(grid [][]byte, x, y int) int {
+	if x < 0 || y < 0 || x >= len(grid[0]) || y >= len(grid) || grid[y][x] != LAND {
+		return 0
+	}
+
+	grid[y][x] = VISITED
+	traverse(grid, x+1, y)
+	traverse(grid, x-1, y)
+	traverse(grid, x, y+1)
+	traverse(grid, x, y-1)
+	return 1
+}
+
+func numIslands(grid [][]byte) int {
+	count := 0
+	for y := range grid {
+		for x := range grid[y] {
+			count += traverse(grid, x, y)
+		}
+	}
+	return count
+}
+
+var _ = numIslands
diff --git a/solutions/5/q530/solution.go b/solutions/5/q530/solution.go
new file mode 100644
index 0000000..673014c
--- /dev/null
+++ b/solutions/5/q530/solution.go
@@ -0,0 +1,37 @@
+package q530
+
+import "math"
+
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+func getMinimumDifference(root *TreeNode) int {
+	minDiff := math.MaxInt
+	var last *int
+
+	var check = func(num int) {
+		if last == nil {
+			last = &num
+			return
+		}
+		minDiff = min(minDiff, num-*last)
+		*last = num
+	}
+	var traverse func(node *TreeNode)
+	traverse = func(node *TreeNode) {
+		if node == nil {
+			return
+		}
+		traverse(node.Left)
+		check(node.Val)
+		traverse(node.Right)
+	}
+	traverse(root)
+
+	return minDiff
+}
+
+var _ = getMinimumDifference
diff --git a/solutions/9/q909/solution.go b/solutions/9/q909/solution.go
new file mode 100644
index 0000000..bd1e397
--- /dev/null
+++ b/solutions/9/q909/solution.go
@@ -0,0 +1,50 @@
+package q909
+
+func coord(n, num int) (x, y int) {
+	num -= 1
+	row := num / n
+	y = n - row - 1
+	x = num % n
+	if row%2 == 1 {
+		x = n - 1 - x
+	}
+	return
+}
+
+func snakesAndLadders(board [][]int) int {
+	n, sqN := len(board), len(board)*len(board)
+	leastRolls := make([]int, sqN)
+	if len(leastRolls) == 1 {
+		return 0
+	}
+
+	queue := make([]int, 0, sqN)
+	queue = append(queue, 1)
+	for ; len(queue) > 0; queue = queue[1:] {
+		cur := queue[0]
+		for dist := 1; dist <= 6 && cur+dist <= sqN; dist++ {
+			next := cur + dist
+			x, y := coord(n, next)
+			if board[y][x] != -1 {
+				next = board[y][x]
+			}
+			rolls := leastRolls[cur-1] + 1
+
+			if (next > 1 && leastRolls[next-1] == 0) || rolls < leastRolls[next-1] {
+				leastRolls[next-1] = rolls
+				if next == sqN {
+					return rolls
+				}
+				queue = append(queue, next)
+			}
+		}
+	}
+
+	l := leastRolls[sqN-1]
+	if l == 0 {
+		return -1
+	}
+	return 0
+}
+
+var _ = snakesAndLadders