description: It is a simplified version of problem F2. The difference between them is the constraints (F1: k ≤ 2, F2: k ≤ 10).
  
  You are given an integer n. Find the minimum integer x such that x ≥ n and the number x is k-beautiful.
  
  A number is called k-beautiful if its decimal representation having no leading zeroes contains no more than k different digits. E.g. if k = 2, the numbers 3434443, 55550, 777 and 21 are k-beautiful whereas the numbers 120, 445435 and 998244353 are not.
  
  Input
  
  The first line contains one integer t (1 ≤ t ≤ 10^4) — the number of test cases. Then t test cases follow.
  
  Each test case consists of one line containing two integers n and k (1 ≤ n ≤ 10^9, 1 ≤ k ≤ 2).
  
  Output
  
  For each test case output on a separate line x — the minimum k-beautiful integer such that x ≥ n.
  
  Example
  
  Input
  
  
  4
  1 1
  221 2
  177890 2
  998244353 1
  
  
  Output
  
  
  1
  221
  181111
  999999999
solution: #include <bits/stdc++.h>
  using namespace std;
  #pragma GCC optimize("O3")
  const int maxl = 9;
  int a[maxl + 1], b[maxl + 1];
  int len, k;
  void prepare(int x) {
    vector<int> p;
    while (x > 0) {
      p.push_back(x % 10);
      x /= 10;
    }
    len = p.size();
    reverse(p.begin(), p.end());
    for (int i = 1; i <= len; i++) {
      a[i] = p[i - 1];
    }
  }
  bool reach = false;
  int cntBit(int n) {
    int cnt = 0;
    while (n) {
      n &= (n - 1);
      cnt++;
    }
    return cnt;
  }
  void print() {
    for (int i = 1; i <= len; i++) {
      cout << b[i];
    }
    cout << '\n';
  }
  void dp(int pos, int flag, int mask) {
    if (reach) {
      return;
    }
    if (cntBit(mask) > k) {
      return;
    }
    if (pos > len) {
      print();
      reach = true;
      return;
    }
    int mini;
    if (flag == 0) {
      mini = 0;
    } else {
      mini = a[pos];
    }
    for (int i = mini; i <= 9; i++) {
      b[pos] = i;
      if (i == mini) {
        int newMask = mask | (1 << i);
        dp(pos + 1, flag, newMask);
      } else {
        int newMask = mask | (1 << i);
        dp(pos + 1, 0, newMask);
      }
    }
  }
  int main() {
    if (fopen(""
              ".INP",
              "r")) {
      freopen(
          ""
          ".INP",
          "r", stdin);
    }
    int t;
    cin >> t;
    for (int co = 0; co < t; co++) {
      reach = false;
      int x;
      cin >> x;
      cin >> k;
      if (x == 1e9) {
        if (k == 1) {
          cout << 1111111111;
        } else {
          cout << x;
        }
        cout << '\n';
        continue;
      }
      prepare(x);
      dp(1, 1, 0);
    }
  }
  