chore: add hackerrank solutions

hacker-rank/tree-height-of-a-binary-tree/main.go

@@ -0,0 +1,67 @@
+package main
+import (
+    "fmt"
+    "bufio"
+    "strconv"
+    "strings"
+    "os"
+)
+
+func main() {
+    var n int
+    var tree *node
+    scanner := bufio.NewScanner(os.Stdin)
+    for scanner.Scan() {
+        text := scanner.Text()
+        if n == 0 {
+            n, _ = strconv.Atoi(text)
+            continue
+        }
+        for _, s := range strings.Fields(text) {
+            if v, err := strconv.Atoi(s); err == nil {
+                tree = insert(tree, &node{value:v})
+            }
+        }
+    }
+    fmt.Println(height(tree, 0))
+}
+
+type node struct{
+    value int
+    left *node
+    right *node
+}
+
+func insert(root, n *node) *node {
+    if root == nil {
+        return n
+    }
+    if n.value < root.value {
+        root.left = insert(root.left, n)
+        return root
+    }
+    root.right = insert(root.right, n)
+    return root
+}
+
+func height(root *node, currentHeight int) int {
+    if root == nil {
+        return -1
+    }
+
+    maxHeight := currentHeight
+
+    if root.left != nil {
+       if nh := height(root.left, currentHeight+1); nh > maxHeight {
+           maxHeight = nh
+       } 
+    }
+
+    if root.right != nil {
+       if nh := height(root.right, currentHeight+1); nh > maxHeight {
+           maxHeight = nh
+       } 
+    }
+
+    return maxHeight
+}