Lemonade Change

<-E 860> Lemonade Change

class Solution {
  
public:
    bool lemonadeChange(vector<int>& bills) {
      int five = 0, ten = 0;
      for (int &i : bills) {
          if (i == 5) five++;
          else if (i == 10) five--, ten++;
          else if (ten > 0) ten--, five--;
          else five -= 3;
          if (five < 0) return false;
      }
      return true;
    }
};