Solution.go

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func findMode(root *TreeNode) []int {
	mx, cnt := 0, 0
	var prev *TreeNode
	var ans []int
	var dfs func(root *TreeNode)
	dfs = func(root *TreeNode) {
		if root == nil {
			return
		}
		dfs(root.Left)
		if prev != nil && prev.Val == root.Val {
			cnt++
		} else {
			cnt = 1
		}
		if cnt > mx {
			ans = []int{root.Val}
			mx = cnt
		} else if cnt == mx {
			ans = append(ans, root.Val)
		}
		prev = root
		dfs(root.Right)
	}
	dfs(root)
	return ans
}