[LeetCode] 726. 原子的数量

大模拟。。。烦这种题
遇到括号匹配的题目，用栈就对了。此题需要栈+Map
没啥难度，写了半天，Debug几个用例后，1A过了

class Solution {
    class Atom {
        String s;
        int cnt = 1;

        Atom(String s, int cnt) {
            this.s = s;
            if (cnt == 0) cnt = 1;
            this.cnt = cnt;
        }
    }

    public String countOfAtoms(String formula) {
        Stack<Atom> stack = new Stack<>();
        Map<String, Atom> map = new HashMap<>();
        int n = formula.length();

        Atom b = new Atom("(", 0);

        String tmp = "";
        int cnt = 0;
        for (int i = 0; i < n; i++) {
            char c = formula.charAt(i);
            if (c >= 'a' && c <= 'z') {
                tmp += c;
                continue;
            }

            if (c >= '0' && c <= '9') {
                cnt *= 10;
                cnt += c - '0';
                continue;
            }

            if (c >= 'A' && c <= 'Z') {
                if ("".equals(tmp)) {
                    tmp += c;
                } else {
                    if (tmp.length() > 0)
                        stack.push(new Atom(tmp, cnt));
                    tmp = "" + c;
                    cnt = 0;
                }
                continue;
            }


            if (c == '(') {
                if (tmp.length() > 0)
                    stack.push(new Atom(tmp, cnt));
                tmp = "";
                cnt = 0;
                stack.push(b);
                continue;
            }

            if (c == ')') {
                if (tmp.length() > 0)
                    stack.push(new Atom(tmp, cnt));
                tmp = "";
                cnt = 0;

                i++;
                while (i < n) {
                    c = formula.charAt(i);
                    if (c >= '0' && c <= '9') {
                        cnt *= 10;
                        cnt += c - '0';
                    } else {
                        break;
                    }
                    i++;
                }
                i--;
                if (cnt == 0) cnt = 1;

                List<Atom> list = new ArrayList<>();
                while (true) {
                    Atom pop = stack.pop();
                    if (pop.s.equals("(")) break;
                    pop.cnt *= cnt;
                    list.add(pop);
                }
                stack.addAll(list);
                cnt = 0;
            }
        }
        if (tmp.length() > 0)
            stack.push(new Atom(tmp, cnt));

        List<Atom> ans = new ArrayList<>(stack);
        for (Atom an : ans) {
            if (map.containsKey(an.s)) {
                map.get(an.s).cnt += an.cnt;
            } else {
                map.put(an.s, an);
            }
        }
        Stream<Atom> sorted = map.values().stream().sorted(Comparator.comparing(o -> o.s));

        StringBuilder ret = new StringBuilder();
        sorted.forEach(an->{
            ret.append(an.s);
            if (an.cnt > 1) ret.append(an.cnt);
        });

        return ret.toString();
    }
}