add new solutions

solutions/1/q103/solution.go

@@ -0,0 +1,55 @@
+package q103
+
+import "slices"
+
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+func zigzagLevelOrder(root *TreeNode) [][]int {
+	ret := [][]int{}
+	if root == nil {
+		return ret
+	}
+
+	dpth := 1
+	buf := make([]int, 512)
+	row := buf[:0]
+
+	type qElem struct {
+		depth int
+		node  *TreeNode
+	}
+	queue := make([]qElem, 0, 256)
+	queue = append(queue, qElem{depth: 1, node: root})
+	for ; len(queue) > 0; queue = queue[1:] {
+		c := queue[0]
+		if c.depth > dpth {
+			if dpth%2 == 0 {
+				slices.Reverse(row)
+			}
+			ret = append(ret, make([]int, len(row)))
+			copy(ret[len(ret)-1], row)
+
+			dpth = c.depth
+			row = buf[:0]
+		}
+
+		row = append(row, c.node.Val)
+		if c.node.Left != nil {
+			queue = append(queue, qElem{depth: c.depth + 1, node: c.node.Left})
+		}
+		if c.node.Right != nil {
+			queue = append(queue, qElem{depth: c.depth + 1, node: c.node.Right})
+		}
+	}
+	if dpth%2 == 0 {
+		slices.Reverse(row)
+	}
+	ret = append(ret, row)
+	return ret
+}
+
+var _ = zigzagLevelOrder