<p>Given a positive integer <code>n</code>, find <em>the smallest integer which has exactly the same digits existing in the integer</em> <code>n</code> <em>and is greater in value than</em> <code>n</code>. If no such positive integer exists, return <code>-1</code>.</p>

<p><strong>Note</strong> that the returned integer should fit in <strong>32-bit integer</strong>, if there is a valid answer but it does not fit in <strong>32-bit integer</strong>, return <code>-1</code>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<pre><strong>Input:</strong> n = 12
<strong>Output:</strong> 21
</pre><p><strong class="example">Example 2:</strong></p>
<pre><strong>Input:</strong> n = 21
<strong>Output:</strong> -1
</pre>
<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= n &lt;= 2<sup>31</sup> - 1</code></li>
</ul>

class Solution {
public:
    int nextGreaterElement(int n) {
        string num = to_string(n);
        for(int i=num.size()-1; i>=0; i--){
            if(num[i] < num[i+1]){
                sort(num.begin()+i+1, num.end());
                auto itr = upper_bound(num.begin()+i+1, num.end(), num[i]);
                swap(num[i], *itr);
                sort(num.begin()+i+1, num.end());
                auto ix = stoll(num);
                if(ix > INT_MAX){
                    return -1;
                }
                return (int)ix;
            }
        }

        return -1;
    }
};
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