Deleting digits

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

using ll = long long;
constexpr int INF = 1'000'000'000; // 1e9
constexpr ll LINF = 1'000'000'000'000'000'000LL; // 1e18

unordered_set<int> digits(int n) {
    unordered_set<int> set;
    for (;n > 0; n/=10) {
        set.insert(n%10);
    }
    set.erase(0);
    return set;
}

void solve() {
    int n;
    cin >> n;

    array<int, 1'000'001> steps = {};
    
    steps[0]=0;
    int m = 0;
    for(int i = 1; i<=n; i++) {
        auto set = digits(i);
        m = INF;
        for (auto s: set) {
            if (i - s >= 0) {
                m = min(m, steps[i - s]);
            }
        }
        steps[i] = m + 1;
    }
    cout << steps[n];
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    solve();

    return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED