Leetcode 题目解析之 Different Ways to Add Parentheses

(2*(3-(4*5))) = -34
((2*3)-(4*5)) = -14
((2*(3-4))*5) = -10
(2*((3-4)*5)) = -10
(((2*3)-4)*5) = 10

    public List<Integer> diffWaysToCompute(String input) {
        List<Integer> rt = new LinkedList<Integer>();
        int len = input.length();
        for (int i = 0; i < len; i++) {
            if (input.charAt(i) == '-' || input.charAt(i) == '*'
                    || input.charAt(i) == '+') {
                String part1 = input.substring(0, i);
                String part2 = input.substring(i + 1);
                List<Integer> part1Ret = diffWaysToCompute(part1);
                List<Integer> part2Ret = diffWaysToCompute(part2);
                for (Integer p1 : part1Ret) {
                    for (Integer p2 : part2Ret) {
                        int c = 0;
                        switch (input.charAt(i)) {
                        case '+':
                            c = p1 + p2;
                            break;
                        case '-':
                            c = p1 - p2;
                            break;
                        case '*':
                            c = p1 * p2;
                        }
                        rt.add(c);
                    }
                }
            }
        }
        if (rt.size() == 0) {
            rt.add(Integer.valueOf(input));
        }
        return rt;
    }