Golang正整数指定规则排序算法问题分析

package huawei
import (
    "errors"
    "fmt"
    "strconv"
    "strings"
)
func Test6Base() {
    s := "2115 22 2128 3115 4119 2016 2119"
    findIndex := 2
    result, err := findString(s, findIndex)
    if err == nil {
        fmt.Println("result:", result)
    } else {
        fmt.Println("Error:", err.Error())
    }
}
//将resString按照指定规则排序，然后返回索引为findIndex位置的字符串
func findString(resString string, findIndex int) (result int, err error) {
    if resString == "" {
        return -1, errors.New("Param resString is an empty string.")
    }
    numsStr := strings.Fields(resString)
    if findIndex < 0 || findIndex > len(numsStr)-1 {
        return -1, errors.New("Param findIndex is invalid.")
    }
    numsInt := convertToInt(numsStr)
    //冒泡排序(稳定)
    var change bool = false
    for i := 0; i < len(numsInt)-1; i++ {
        change = false
        for j := 1; j < len(numsInt)-i; j++ {
            if numsInt[j]%1000 < numsInt[j-1]%1000 {
                change = true
                numsInt[j], numsInt[j-1] = numsInt[j-1], numsInt[j]
            }
        }
        if !change {
            break
        }
    }
    fmt.Println(numsInt)
    return numsInt[findIndex], nil
}
//将[]string转为[]int
func convertToInt(numsStr []string) []int {
    numsInt := make([]int, len(numsStr))
    for i, v := range numsStr {
        n, err := strconv.Atoi(v)
        checkError(err, "string to integer")
        numsInt[i] = n
    }
    return numsInt
}