<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>

class Solution {
 public:
  vector<int> diffWaysToCompute(string expression) {
    return ways(expression, {});
  }

 private:
  vector<int> ways(const string& s, unordered_map<string, vector<int>>&& mem) {
    if (const auto it = mem.find(s); it != mem.cend())
      return it->second;

    vector<int> ans;

    for (int i = 0; i < s.length(); ++i)
      if (ispunct(s[i]))
        for (const int a : ways(s.substr(0, i), std::move(mem)))
          for (const int b : ways(s.substr(i + 1), std::move(mem)))
            if (s[i] == '+')
              ans.push_back(a + b);
            else if (s[i] == '-')
              ans.push_back(a - b);
            else
              ans.push_back(a * b);

    return mem[s] = (ans.empty() ? vector<int>{stoi(s)} : ans);
  }
};


        
    

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