如何打印给定数字n的大小为m的所有子序列？

如何解决如何打印给定数字n的大小为m的所有子序列？

针对以下问题：

一个数字的子序列是该数字的一系列（不一定是连续的）数字。例如，12345的子序列包括123、234、124、245等。您的任务是生成低于特定长度的子序列。

def generate_subseq(n,m):
    """
    Print all subsequence of length at most m that can be found in the given number n.
    For example,for n = 20125 and m = 3,we have that the subsequences are
        201
        202
        205
        212
        215
        225
        012
        015
        025
        125
   

    >>> generate_subseq(20125,3)
        201
        202
        205
        212
        215
        225
        012
        015
        025
        125
     >>> generate_subseq(20125,5)
        20125
    """

---

下面是无效的解决方案：

package main

import (
    "fmt"
    "strconv"
)

func generateSubSequence(n int,subSequenceSize int) []int {

    digitSequence := intToSequenceOfDigits(n) // [2,1,2,5]

    var f func([]int,int,int) []int
    f = func(digitSequence []int,pickingIndex int,currentSubSequenceSize int) []int {

        if pickingIndex+1 == currentSubSequenceSize {
            value := sequenceOfDigitsToInt(digitSequence[0:currentSubSequenceSize])
            return []int{value}
        }

        if currentSubSequenceSize == 0 {
            return []int{}
        }

        digit := digitSequence[pickingIndex]

        withM := mapDigit(f(digitSequence,pickingIndex-1,currentSubSequenceSize-1),digit)
        withoutM := f(digitSequence,currentSubSequenceSize)

        return append(withM,withoutM...)
    }

    return f(digitSequence,len(digitSequence)-1,subSequenceSize)
}

func mapDigit(slice []int,digit int) []int {
    result := make([]int,len(slice))
    for i,value := range slice {
        result[i] = value*10 + digit
    }
    return result
}

func sequenceOfDigitsToInt(digits []int) int {
    result := 0
    for _,value := range digits {
        result = result*10 + value
    }
    return result
}

func intToSequenceOfDigits(n int) []int { // [2,5]
    var convert func(int) []int
    sequence := []int{}
    convert = func(n int) []int {
        if n != 0 {
            digit := n % 10
            sequence = append([]int{digit},sequence...)
            convert(n / 10)
        }
        return sequence
    }
    return convert(n)
}


func main() {
    fmt.Println(generateSubSequence(20125,3))
}

---

实际输出为：[225 215 205 212 202 201]

预期输出为：[201 202 205 212 215 225 012 015 025 125]

为什么实际输出缺少某些子序列？像125等...

解决方法

像这样？修改其他answer：

function f(s,i,l){
  if (i + 1 == l)
    return [s.substr(0,l)];

  if (!l)
    return [''];
    
  const left = f(s,i - 1,l);
  const right = f(s,l - 1);

  return left.concat(
    right.map(x => x + s[i]));
}

var input = [
  ['20125',3],['12345',3]
];

for (let [s,l] of input){
  console.log(s + ',l: ' + l);
  console.log(JSON.stringify(f(s,s.length-1,l)));
  console.log('');
}