C++ 代码

#include<bits/stdc++.h>
using namespace std;

string solution(string s, long long n) {
    if (s.length() == 0) return "";
    if (n == 0) return s;
    if (s.length() == 1 && n == 1) return "";

    int len = s.length();
    int minNum = INT_MAX;
    //前n+1个数
    for (int i = 0; i < n + 1; i++) {
        minNum = min(minNum, s[i] - '0');
    }
    //minNum前的都删掉
    int p = 0;
    while (s[p] - '0' > minNum) {
        p++;
        n--;
    }
    //截取
    s = s.substr(p, len - p + 1);
    //删了
    if (s.length() < len) return solution(s, n);
    //没删
    else {
        char c = s[0];
        s = s.substr(1, len-1);
        return (c + solution(s, n));
    }
}

int main()
{
    int n;
    string s;
    cin >> s >> n;
    //从n+1里面选个最小的,前面的都删掉
    cout << solution(s, n);
}