Different Ways to Add Parentheses

Desicription

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:

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Input: "2-1-1"
Output: [0, 2]
Explanation:
((2-1)-1) = 0
(2-(1-1)) = 2

Example 2:

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Input: "2*3-4*5"
Output: [-34, -14, -10, -10, 10]
Explanation:
(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

Solution

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class Solution {
public:
vector<int> diffWaysToCompute(const string &input) {
vector<int> res;
for(int i = 0; input[i]; i++) {
if(input[i] == '+' || input[i] == '-' || input[i] == '*') {
vector<int> nums_1 = diffWaysToCompute(input.substr(0, static_cast<unsigned int>(i)));
vector<int> nums_2 = diffWaysToCompute(input.substr(static_cast<unsigned int>(i + 1)));
for(const auto& a : nums_1) {
for(const auto& b : nums_2) {
if(input[i] == '+') {
res.push_back(a + b);
} else if(input[i] == '-') {
res.push_back(a - b);
} else {
res.push_back(a * b);
}
}
}
}
}
if(res.empty()) {
res.push_back(atoi(input.c_str()));
}
return res;
}
};