Leetcode 241. Different Ways to Add Parentheses (Medium) (cpp)

Leetcode 241. Different Ways to Add Parentheses (Medium) (cpp)

Tag: Divide and Conquer

Difficulty: Medium

/*241. Different Ways to Add Parentheses (Medium)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 1Input: "2-1-1".((2-1)-1) = 0(2-(1-1)) = 2Output: [0, 2]Example 2Input: "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) = 10Output: [-34, -14, -10, -10, 10]*/class Solution {private:int _len;vector<int> calculate(const string& input, int st, int ed) {vector<int> res;if (st > ed) return res;for (int i = st; i <= ed; i++) {if (!isdigit(input[i])) {vector<int> l = calculate(input, st, i - 1), r = calculate(input, i + 1, ed);for (int j = 0; j < l.size(); j++) {for (int k = 0; k < r.size(); k++) {switch(input[i]) {case '-': res.push_back(l[j] - r[k]); break;case '+': res.push_back(l[j] + r[k]); break;case '*': res.push_back(l[j] * r[k]); break;}}}}}if (res.empty()) res.push_back(stoi(input.substr(st, ed - st + 1)));return res;}public:vector<int> diffWaysToCompute(string input) {int _len = input.length();return calculate(input, 0, _len - 1);}};