Language: C++

 #include <iostream>
#include <cstdio>
#include <algorithm>
#include <cmath>
#include <vector>
#include <list>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <cctype>
#include <cassert>
#include <climits>
#include <string>
#include <bitset>
#include <cfloat>
#include <unordered_set>
#include <iomanip>
using namespace std;
typedef long double ld;
typedef long long int ll;
typedef unsigned long long int ull;
typedef pair<int,int> pii;
typedef vector<int> vi;
typedef vector<char> vc;
typedef vector<bool> vb;
typedef vector<double> vd;
typedef vector<string> vs;
typedef vector<ll> vll;
typedef vector<pair<int,int> > vpii;
typedef vector<vector<int> > vvi;
typedef vector<vector<char> > vvc;
typedef vector<vector<string> > vvs;
typedef vector<vector<ll> > vvll;
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define rrep(i,n) for(int i = 1; i <= (n); ++i)
#define irep(it, stl) for(auto it = stl.begin(); it != stl.end(); it++)
#define drep(i,n) for(int i = (n) - 1; i >= 0; --i)
#define fin(ans) cout << (ans) << endl
#define mp(p,q) make_pair(p, q)
#define pb(n) push_back(n)
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define Sort(a) sort(a.begin(), a.end())
#define Rort(a) sort(a.rbegin(), a.rend())
#define MATHPI acos(-1)
int dx8[8] = {1, 0, -1, 0, 1, -1, -1, 1};
int dy8[8] = {0, 1, 0, -1, 1, 1, -1, -1};
int dx4[4] = {1, 0, -1, 0};
int dy4[4] = {0, 1, 0, -1};
template <class T> inline bool chmax(T& a,T b){if(a<b){a=b;return 1;} return 0;}
template <class T> inline bool chmin(T& a,T b){if(a>b){a=b;return 1;} return 0;}
template<typename A, size_t N, typename T> void Fill(A (&array)[N], const T &val){ fill((T*)array, (T*)(array+N), val); }
struct io{io(){ios::sync_with_stdio(false);cin.tie(0);}};
const int INF = INT_MAX;
const ll LLINF = 1LL<<60;
const ll MOD = 1000000007;
const double EPS = 1e-9;



int main(void) {
   ll N,S;
   cin >> N >> S;
   ll ans =0;
   rep(i,10){
       rep(j,10){
           rep(k,10){
               bool fi = false,se =false;//フラグリセット
               //例えば今の暗証番号が112として,Sのどこかに連続する112があればいい
               rep(s,N){
                   if(!fi&&S[s] == i + '0'){
                       fi = true;//最初の数字を発見
                       continue;
                   }
                   //最初の数字が発見されて、かつ二番目が未発見、で一致
                   if(fi && !se && S[s] == j + '0'){
                       se = true;
                       continue;
                   }
                   //最初と二番目を発見、で三番目が一致
                   if(fi && se && S[s] == k+'0'){
                       ans++;
                       break;
                   }
               }
           }
       }
   }
   fin(ans);
    
}

Compiler output:
a.cc: In function 'int main()':
a.cc:72:29: error: invalid types 'll {aka long long int}[int]' for array subscript
   72 |                    if(!fi&&S[s] == i + '0'){
      |                             ^
a.cc:77:37: error: invalid types 'll {aka long long int}[int]' for array subscript
   77 |                    if(fi && !se && S[s] == j + '0'){
      |                                     ^
a.cc:82:36: error: invalid types 'll {aka long long int}[int]' for array subscript
   82 |                    if(fi && se && S[s] == k+'0'){
      |                                    ^