fenzhi

class Solution {
    public List<Integer> diffWaysToCompute(String input)
    {
        List<Integer> ways = new ArrayList<>();
        for (int i = 0; i < input.length(); i++)
        {
            char c = input.charAt(i);
            if (c == ‘+‘ || c == ‘-‘ || c == ‘*‘)
            {
                List<Integer> left = diffWaysToCompute(input.substring(0,i));   //
                List<Integer> right = diffWaysToCompute(input.substring(i + 1));
                for (int l:left)
                {
                    for (int r:right)
                    {
                        switch(c)
                        {
                            case ‘+‘:
                                ways.add(l+r);
                                break;
                            case ‘-‘:
                                ways.add(l-r);
                                break;
                            case ‘*‘:
                                ways.add(l*r);
                                break;
                        }
                    }
                }
            }
        } 
        if (ways.size() == 0)
        {
            ways.add(Integer.valueOf(input));
        }
        return ways;
    }
}