<p>You are given an integer <code>num</code>. You will apply the following steps exactly <strong>two</strong> times:</p>

<ul>
	<li>Pick a digit <code>x (0 &lt;= x &lt;= 9)</code>.</li>
	<li>Pick another digit <code>y (0 &lt;= y &lt;= 9)</code>. The digit <code>y</code> can be equal to <code>x</code>.</li>
	<li>Replace all the occurrences of <code>x</code> in the decimal representation of <code>num</code> by <code>y</code>.</li>
	<li>The new integer <strong>cannot</strong> have any leading zeros, also the new integer <strong>cannot</strong> be 0.</li>
</ul>

<p>Let <code>a</code> and <code>b</code> be the results of applying the operations to <code>num</code> the first and second times, respectively.</p>

<p>Return <em>the max difference</em> between <code>a</code> and <code>b</code>.</p>

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

<pre>
<strong>Input:</strong> num = 555
<strong>Output:</strong> 888
<strong>Explanation:</strong> The first time pick x = 5 and y = 9 and store the new integer in a.
The second time pick x = 5 and y = 1 and store the new integer in b.
We have now a = 999 and b = 111 and max difference = 888
</pre>

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

<pre>
<strong>Input:</strong> num = 9
<strong>Output:</strong> 8
<strong>Explanation:</strong> The first time pick x = 9 and y = 9 and store the new integer in a.
The second time pick x = 9 and y = 1 and store the new integer in b.
We have now a = 9 and b = 1 and max difference = 8
</pre>

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

<ul>
	<li><code>1 &lt;= num &lt;= 10<sup>8</sup></code></li>
</ul>

class Solution {
public:
    int maxDiff(int num) {
        string numStr = to_string(num);
        string maxNumStr = numStr;
        string minNumStr = numStr;
        
        // Find the first digit that is not '9' for maxNumStr replacement
        for (char& c : maxNumStr) {
            if (c != '9') {
                char toReplace = c;
                for (char& ch : maxNumStr) {
                    if (ch == toReplace) {
                        ch = '9';
                    }
                }
                break;
            }
        }
        
        // Check if the first digit is '1', then replace other digits accordingly
        if (minNumStr[0] != '1') {
            char toReplace = minNumStr[0];
            for (char& c : minNumStr) {
                if (c == toReplace) {
                    c = '1';
                }
            }
        } else {
            for (int i = 1; i < minNumStr.size(); ++i) {
                if (minNumStr[i] != '0' && minNumStr[i] != '1') {
                    char toReplace = minNumStr[i];
                    for (int j = i; j < minNumStr.size(); ++j) {
                        if (minNumStr[j] == toReplace) {
                            minNumStr[j] = '0';
                        }
                    }
                    break;
                }
            }
        }
        
        int maxNum = stoi(maxNumStr);
        int minNum = stoi(minNumStr);
        
        return maxNum - minNum;
    }
};
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