solution.go

package main

import "fmt"

// TreeNode is a binary tree node.
type TreeNode struct {
	Val   int
	Left  *TreeNode
	Right *TreeNode
}

func mergeTrees(t1 *TreeNode, t2 *TreeNode) *TreeNode {
	if t1 == nil {
		return t2
	}
	if t2 == nil {
		return t1
	}
	t1.Val += t2.Val
	t1.Left = mergeTrees(t1.Left, t2.Left)
	t1.Right = mergeTrees(t1.Right, t2.Right)
	return t1
}

func main() {
	t1 := &TreeNode{1, &TreeNode{2, &TreeNode{4, nil, nil}, &TreeNode{5, nil, nil}}, &TreeNode{3, nil, nil}}
	t2 := &TreeNode{2, &TreeNode{1, nil, &TreeNode{4, nil, nil}}, &TreeNode{3, nil, &TreeNode{7, nil, nil}}}
	fmt.Println(mergeTrees(t1, t2))
}