find-common-characters.cc

// Find Common Characters
#define FOR(i, a, b) for (remove_cv<remove_reference<decltype(b)>::type>::type i = (a); i < (b); i++)
#define REP(i, n) FOR(i, 0, n)

class Solution {
public:
  vector<string> commonChars(vector<string>& A) {
    int r[26], c[26];
    fill_n(r, 26, INT_MAX);
    for (auto &s: A) {
      fill_n(c, 26, 0);
      for (char a: s) c[a-'a']++;
      REP(i, 26) r[i] = min(r[i], c[i]);
    }
    vector<string> s;
    REP(i, 26) while (r[i]--) s.emplace_back(1, i+'a');
    return s;
  }
};