101. Symmetric Tree

Author: vfedorovatlas

symmetric-tree/Readme.md

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+# Problem: 101. Symmetric Tree
+
+Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).
+
+For example, this binary tree [1,2,2,3,4,4,3] is symmetric:
+
+```go
+   1
+   / \
+  2   2
+ / \ / \
+3  4 4  3
+```
+
+But the following [1,2,2,null,3,null,3] is not:
+
+```go
+    1
+   / \
+  2   2
+   \   \
+   3    3
+```

symmetric-tree/main.go

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+package symmetrictree
+
+// TreeNode data structure
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+// Explanation: https://leetcode.com/articles/symmetric-tree/
+func isSymmetric(root *TreeNode) bool {
+	return isMirror(root, root)
+}
+
+func isMirror(left *TreeNode, right *TreeNode) bool {
+	if left == nil && right == nil {
+		return true
+	}
+	if left == nil || right == nil {
+		return false
+	}
+	ret := left.Val == right.Val &&
+		isMirror(left.Right, right.Left) &&
+		isMirror(left.Left, right.Right)
+	return ret
+}

symmetric-tree/main_test.go

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+package symmetrictree
+
+import (
+	"testing"
+)
+
+func TestMaxDepth(t *testing.T) {
+	testCases := []struct {
+		Input  *TreeNode
+		Output bool
+	}{
+		{
+			Input: &TreeNode{
+				Val: 1,
+				Left: &TreeNode{
+					Val: 2,
+					Left: &TreeNode{
+						Val: 3,
+					},
+					Right: &TreeNode{
+						Val: 4,
+					},
+				},
+				Right: &TreeNode{
+					Val: 2,
+					Left: &TreeNode{
+						Val: 4,
+					},
+					Right: &TreeNode{
+						Val: 3,
+					},
+				},
+			},
+			Output: true,
+		},
+	}
+
+	for _, test := range testCases {
+		out := isSymmetric(test.Input)
+		if !(test.Output == out) {
+			t.Errorf("expected to get %#v, but got %#v", test.Output, out)
+		}
+	}
+}