majority-element-ii.cc

// Majority Element II
class Solution {
public:
  vector<int> majorityElement(vector<int> &a) {
    int y = 0, z = 1, cy = 0, cz = 0;
    for (auto x: a) {
      if (x == y) cy++;
      else if (x == z) cz++;
      else if (! cy) y = x, cy = 1;
      else if (! cz) z = x, cz = 1;
      else cy--, cz--;
    }
    cy = cz = 0;
    for (auto x: a)
      if (x == y) cy++;
      else if (x == z) cz++;
    vector<int> r;
    if (cy > a.size()/3) r.push_back(y);
    if (cz > a.size()/3) r.push_back(z);
    return r;
  }
};