[LeetCode] Different Ways to Add Parentheses

Given a string of numbers and operators, return all possible results from computing all the different possible ways to group numbers and operators. The valid operators are +,- and *.

Example 1

Input: "2-1-1".

((2-1)-1) = 0
(2-(1-1)) = 2

Output: [0, 2]

Example 2

Input: "2*3-4*5"

(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

Output: [-34, -14, -10, -10, 10]

Analysis:

Divide and conquer

class Solution {
    void calculate(vector<int>&res, vector<int>&l,
                   vector<int>&r, char op)
    {
        for(auto e:l)
        {
            for(auto m:r)
            {
                if(op == '+') res.push_back(e+m);
                else if(op == '-') res.push_back(e-m);
                else if(op == '*') res.push_back(e*m);
                else if(op == '/') {
                    if(m!=0)res.push_back(e/m);
                    else res.push_back(e>0?INT_MAX:INT_MIN);
                }
            }
        }
    }
    void solve(vector<int> &res,  const string & input)
    {
        bool found = false;
        for(int i=1;i<input.length();i++)
        {
            if(input[i] == '+' || input[i] == '-'  
                || input[i] == '*' || input[i] == '/')
            {
                vector<int> l, r;
                solve(l, input.substr(0,i));
                solve(r, input.substr(i+1));
                if(!found) found = true;
                calculate(res, l, r, input[i]);
            }
        }
        
        if(!found) res.push_back(stoi(input));
    }
    
public:
    vector<int> diffWaysToCompute(string input) {
        vector<int> res;
        solve(res, input);
        return res;
    }
};