<p>You are given an integer <code>num</code>. You can swap two digits at most once to get the maximum valued number.</p>

<p>Return <em>the maximum valued number you can get</em>.</p>

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

<pre>
<strong>Input:</strong> num = 2736
<strong>Output:</strong> 7236
<strong>Explanation:</strong> Swap the number 2 and the number 7.
</pre>

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

<pre>
<strong>Input:</strong> num = 9973
<strong>Output:</strong> 9973
<strong>Explanation:</strong> No swap.
</pre>

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

<ul>
	<li><code>0 &lt;= num &lt;= 10<sup>8</sup></code></li>
</ul>

class Solution {
public:
    int maximumSwap(int num) {
        
        int a = num; 
        int maxdigit = INT_MIN; 
        string str = ""; 
        while(a>0){
            str+=a%10 + '0'; 
            a = a/10; 
        }
        reverse(str.begin() , str.end()); 
        vector<int> prefix (str.size() , 0); 
        prefix[str.size() - 1] = str.size() - 1; 
        for (int i = str.size() - 2 ; i>=0; i--){
            if(str[i] > str[prefix[i+1]]){
                prefix[i] = i ; 
            }else prefix[i] = prefix[i+1]; 
        }

        for (int i = 0 ; i<str.size() ; i++){
            if(prefix[i] == i || str[i] == str[prefix[i]])continue; 
            else {
                swap(str[i] , str[prefix[i]]); 
                break; 
            }
           
        }

        return stoll(str); 
    }
};
7600