LeetCode-501. Mode in Binary Search Tree (implemented in Golang)

LeetCode question number: 501. Mode in the binary search tree

Given a binary search tree (BST) with the same value, find all modes (the most frequent element) in the BST.
For example:
given BST [1,null,2,2],

   1
    \
     2
    /
   2
Back [2]

note:

Is the output mode, if there is no duplicate value, then all output!

Problem-solving ideas
1. Pre-order traversal and count all the repeated numbers and store them in the map
2. Traverse the map and enter the mode

Code:

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func findMode(root *TreeNode) []int {
    var m = make(map[int]int)
    m = traverses(m, root)
    var list1 []int
    var list2 []int
    var max int = 1
    for k, v := range m {
        if v > max {
            max = v
            //清空与max值相等而追加进list2中的元素，保证进list2中的重复值必须是最大或等大的
            list2 = []int{}
        }
        //追加与max相等的元素
        if v == max && v != 1 {
            list2 = append(list2, k)
        }
        //目的是考虑没有重复值的情况下，直接返回该list1即可
        list1 = append(list1, k)
    }
    //说明没有重复值，都是众数
    if max == 1 {
        return list1
    }
    return list2
}

//先序遍历
func traverses(m map[int]int, node *TreeNode) map[int]int {
    if node == nil {
        return map[int]int{}
    }
    //累加重复值
    m[node.Val]++
    traverses(m, node.Left)
    traverses(m, node.Right)
    return m
}

 Past review:

[1] LeetCode-617. Merging Binary Trees (implemented by Goland)

[2] LeetCode-104. Maximum depth of binary tree (implemented by Goland) 

[3] LeetCode-111. The minimum depth of a binary tree (implemented by Goland)

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