package huawei
import (
    "fmt"
    "sort"
    "strconv"
)
func Test5Base() {
    num := 431492
    degressiveNums := getDegressiveNums(num)
    max := -1
    if len(degressiveNums) > 0 {
        max = getMax(degressiveNums)
    }
    fmt.Println("max:", max)
}
//獲取num的所有遞減數(shù)
func getDegressiveNums(num int) []int {
    if num < 0 {
        return []int{-1}
    }
    degressiveNums := make([]int, 0)
    numStr := strconv.Itoa(num)
    length := len(numStr)
    //長度為i的子串
    for i := 2; i < length; i++ {
        //從j開始截取
        for j := 0; j < length-i+1; j++ {
            //截取數(shù)字
            n, err := strconv.Atoi(numStr[j : j+i])
            checkError(err, "string to integer")
            //是否為遞減數(shù)
            if isDegressive(n) {
                degressiveNums = append(degressiveNums, n)
            }
        }
    }
    return degressiveNums
}
//判斷數(shù)字num是否是遞減數(shù)
func isDegressive(num int) bool {
    weishu := make([]int, 0)
    for num >= 1 {
        n := num % 10
        weishu = append(weishu, n)
        num /= 10
    }
    return sort.IntsAreSorted(weishu)
}
//獲取一個slice中最大的數(shù)
func getMax(nums []int) int {
    if len(nums) == 0 {
        panic("empty slice.")
    }
    max := nums[0]
    for i := 1; i < len(nums); i++ {
        if nums[i] > max {
            max = nums[i]
        }
    }
    return max
}