<p>Given a string <code>expression</code> of numbers and operators, return <em>all possible results from computing all the different possible ways to group numbers and operators</em>. You may return the answer in <strong>any order</strong>.</p>

<p>The test cases are generated such that the output values fit in a 32-bit integer and the number of different results does not exceed <code>10<sup>4</sup></code>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> expression = &quot;2-1-1&quot;
<strong>Output:</strong> [0,2]
<strong>Explanation:</strong>
((2-1)-1) = 0 
(2-(1-1)) = 2
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> expression = &quot;2*3-4*5&quot;
<strong>Output:</strong> [-34,-14,-10,-10,10]
<strong>Explanation:</strong>
(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
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= expression.length &lt;= 20</code></li>
	<li><code>expression</code> consists of digits and the operator <code>&#39;+&#39;</code>, <code>&#39;-&#39;</code>, and <code>&#39;*&#39;</code>.</li>
	<li>All the integer values in the input expression are in the range <code>[0, 99]</code>.</li>
</ul>

#include <vector>
#include <string>
#include <unordered_map>
#include <functional>
#include <iostream>

class Solution {
public:
    std::vector<int> diffWaysToCompute(std::string expression) {
        std::function<std::vector<int>(std::string)> compute = [&](std::string expr) {
            if (std::all_of(expr.begin(), expr.end(), ::isdigit) || 
                (expr[0] == '-' && std::all_of(expr.begin() + 1, expr.end(), ::isdigit))) {
                return std::vector<int>{std::stoi(expr)};
            }

            std::vector<int> result;

            for (size_t i = 0; i < expr.size(); ++i) {
                char ch = expr[i];
                if (ch == '+' || ch == '-' || ch == '*') {
                    std::vector<int> left_results = compute(expr.substr(0, i));
                    std::vector<int> right_results = compute(expr.substr(i + 1));
                    for (int left : left_results) {
                        for (int right : right_results) {
                            if (ch == '+') {
                                result.push_back(left + right);
                            } else if (ch == '-') {
                                result.push_back(left - right);
                            } else if (ch == '*') {
                                result.push_back(left * right);
                            }
                        }
                    }
                }
            }

            return result;
        };

        return compute(expression);
    }
};

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