442. 数组中重复的数据

package main
import (
    "fmt"
    "sort"
)
func findDuplicates(nums []int) []int {
    m := make(map[int]int)
    for _,v:=range nums{
        if i,ok:=m[v];ok {
            m[v]=i+1
        }else {
            m[v]=1
        }
    }
    var res []int
    for k,v:=range m{
        if v==2 {
            res = append(res,k)
        }
    }
    sort.Ints(res)
    return res
}
func main() {
    fmt.Println(findDuplicates([]int{4,3,2,7,8,2,3,1}))
}