Merge pull request #78 from arunsathiya/solve/543-diameter-of-binary-…

…tree

543. Diameter Of Binary Tree

src/543-diameter-of-binary-tree/main.go

@@ -0,0 +1,30 @@
+package main
+
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+func diameterOfBinaryTree(root *TreeNode) int {
+	max := 0
+	var depth func(node *TreeNode) int
+	depth = func(node *TreeNode) int {
+		if node == nil {
+			return 0
+		}
+		leftDepth := depth(node.Left)
+		rightDepth := depth(node.Right)
+		max = maxHelper(max, leftDepth+rightDepth)
+		return 1 + maxHelper(leftDepth, rightDepth)
+	}
+	depth(root)
+	return max
+}
+
+func maxHelper(a, b int) int {
+	if a > b {
+		return a
+	}
+	return b
+}

src/543-diameter-of-binary-tree/main_test.go

@@ -0,0 +1,49 @@
+package main
+
+import "testing"
+
+func TestDiameterOfBinaryTree(t *testing.T) {
+	tests := []struct {
+		root     *TreeNode
+		expected int
+	}{
+		{buildTree([]interface{}{1, 2, 3, 4, 5}), 3},
+		{buildTree([]interface{}{1, 2}), 1},
+		{buildTree([]interface{}{3, 1, nil, nil, 2}), 2},
+	}
+
+	for _, test := range tests {
+		if got := diameterOfBinaryTree(test.root); got != test.expected {
+			t.Errorf("diameterOfBinaryTree() = %d, want %d", got, test.expected)
+		}
+	}
+}
+
+func buildTree(nodes []interface{}) *TreeNode {
+	if len(nodes) == 0 {
+		return nil
+	}
+
+	var root *TreeNode
+	queue := []*TreeNode{}
+	for i, val := range nodes {
+		if val == nil {
+			continue
+		}
+		newNode := &TreeNode{Val: val.(int)}
+		if i == 0 {
+			root = newNode
+			queue = append(queue, newNode)
+			continue
+		}
+		parent := queue[0]
+		if parent.Left == nil {
+			parent.Left = newNode
+		} else if parent.Right == nil {
+			parent.Right = newNode
+			queue = append(queue[:0], queue[1:]...) // Dequeue
+		}
+		queue = append(queue, newNode)
+	}
+	return root
+}