message: Update bulls-and-cows.cpp
diff: class Solution {
  public:
  string getHint(string secret, string guess) {
  - unordered_map<char, int> s_lookup, g_lookup;
  + unordered_map<char, int> lookup;
  int A = 0, B = 0;
  - const int n = min(secret.length(), guess.length());
  - for (int i = 0; i < n; ++i) {
  + for (int i = 0; i < size(secret); ++i) {
  const char s = secret[i];
  const char g = guess[i];
  if (s == g) {
  ++A;
  } else {
  - (s_lookup[g] > 0) ? --s_lookup[g], ++B : ++g_lookup[g];
  - (g_lookup[s] > 0) ? --g_lookup[s], ++B : ++s_lookup[s];
  + B += int(lookup[s]++ < 0) + int(lookup[g]-- > 0);
  }
  }
  return to_string(A).append("A").append(to_string(B)).append("B");
  @@ -37,8 +35,7 @@ public:
  ++B;
  }
  }
  - const int n = min(secret.length(), guess.length());
  - for (int i = 0; i < n; ++i) {
  + for (int i = 0; i < size(secret); ++i) {
  if (secret[i] == guess[i]) {
  ++A, --B;
  }
  