Second Largest Number from Given Number

          45
        /    \
      40       60
    /   \      /  \ 
  20     42   50   70

In given above tree,
if given number n as 70 then result should be 60
if given number n as 60 then result should be 45
if given number n as 43 then result should be 42
if given number n as 15 then result should be NOT FOUND

Implementation

package main

import "fmt"

type Tree struct {
    data  int
    left  *Tree
    right *Tree
}

func main() {
    root := &Tree{data: 45}
    root.left = &Tree{data: 40}
    root.left.left = &Tree{data: 20}
    root.left.right = &Tree{data: 42}

    root.right = &Tree{data: 60}
    root.right.left = &Tree{data: 50}
    root.right.right = &Tree{data: 70}
    result := secondLarge(root, 80)
    if result == nil {
        fmt.Println("Not Found")
    } else {
        fmt.Println(*result)
    }

}

func secondLarge(root *Tree, n int) *int {
    if root == nil {
        return nil
    }
    var result *int
    if root.data < n {
        result = secondLarge(root.right, n)
    } else if root.data > n {
        result = secondLarge(root.left, n)
    }
    if result == nil || *result >= n {
        if root.data > n {
            return nil
        }
        return &root.data
    }
    return result
}