leetcode

0 class Solution {

1 enum Type {

2 Atom,

3 Number,

4 Extra,

5 };

6

7 public:

8 string countOfAtoms(const string &formula) const {

9 string res;

10

11 vector<string> tokens;

12 string crnt;

13 Type type = Extra;

14

15 for (const char c : formula) {

16 if (c == '(' || c == ')') {

17 tokens.push_back(crnt);

18 type = Extra;

19 crnt = "";

20 } else if (isdigit(c)) {

21 if (type != Number) {

22 tokens.push_back(crnt);

23 type = Number;

24 crnt = "";

25 }

26 } else {

27 if (type != Atom || isupper(c)) {

28 tokens.push_back(crnt);

29 type = Atom;

30 crnt = "";

31 }

32 }

33

34 crnt += c;

35 }

36 tokens.push_back(crnt);

37

38 using map_t = map<string, long long>;

39

40 map_t last_count;

41 stack<map_t> count;

42 string last_atom;

43

44 type = Extra;

45 count.push({});

46 tokens.erase(tokens.begin());

47 for (const auto &token : tokens) {

48 if (token[0] == '(') {

49 if (type == Atom) count.top()[last_atom]++;

50 count.push({});

51 type = Extra;

52 } else if (token[0] == ')') {

53 if (type == Atom) count.top()[last_atom]++;

54 last_count = std::move(count.top());

55 count.pop();

56 type = Extra;

57 } else {

58 if (isdigit(token[0])) {

59 const auto value = stoll(token);

60 if (type == Extra) {

61 for (auto &[_, v] : last_count)

62 v *= value;

63 } else {

64 count.top()[last_atom] += value;

65 }

66 }

67

68 if (type == Extra) {

69 for (const auto &[k, v] : last_count) {

70 count.top()[k] += v;

71 }

72 last_count = {};

73 }

74

75 if (isdigit(token[0]))

76 type = Number;

77 else {

78 if (type == Atom) count.top()[last_atom]++;

79 last_atom = token;

80 type = Atom;

81 }

82 }

83 }

84

85 if (type == Extra) {

86 for (const auto &[k, v] : last_count)

87 count.top()[k] += v;

88 } else if (type == Atom)

89 count.top()[last_atom]++;

90

91 for (const auto &[e, c] : count.top()) {

92 res += e;

93 if (c > 1) res += to_string(c);

94 }

95

96 return res;

97 }

98 };