<p>Given an array&nbsp;of <code>intervals</code>&nbsp;where <code>intervals[i] = [start<sub>i</sub>, end<sub>i</sub>]</code>, merge all overlapping intervals, and return <em>an array of the non-overlapping intervals that cover all the intervals in the input</em>.</p>

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

<pre>
<strong>Input:</strong> intervals = [[1,3],[2,6],[8,10],[15,18]]
<strong>Output:</strong> [[1,6],[8,10],[15,18]]
<strong>Explanation:</strong> Since intervals [1,3] and [2,6] overlap, merge them into [1,6].
</pre>

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

<pre>
<strong>Input:</strong> intervals = [[1,4],[4,5]]
<strong>Output:</strong> [[1,5]]
<strong>Explanation:</strong> Intervals [1,4] and [4,5] are considered overlapping.
</pre>

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

<ul>
	<li><code>1 &lt;= intervals.length &lt;= 10<sup>4</sup></code></li>
	<li><code>intervals[i].length == 2</code></li>
	<li><code>0 &lt;= start<sub>i</sub> &lt;= end<sub>i</sub> &lt;= 10<sup>4</sup></code></li>
</ul>

bool compareBegin( vector<int>& vec1, vector<int> & vec2 )
{
    return vec1.front() < vec2.front();
}

class Solution
{
public:
    vector<vector<int>> merge( vector<vector<int>> & intervals )
    {
        ios_base::sync_with_stdio(false);
        cin.tie(0);
        vector<vector<int>> result;

        sort( intervals.begin(), intervals.end(), compareBegin );

        int CurrentStart = intervals[0][0];
        int CurrentEnd   = intervals[0][1];

        if( intervals.empty() )
        {
            return result;
        }

        for( int i = 1; i < intervals.size(); ++i )
        {
            int NewStart = intervals[i][0];
            int NewEnd   = intervals[i][1];

            if( CurrentEnd >= NewStart  )
            {
                CurrentEnd = max( CurrentEnd, NewEnd );
            }
            else
            {
                result.push_back( { CurrentStart, CurrentEnd } );

                CurrentStart = NewStart;
                CurrentEnd   = NewEnd;
            }
        }

        result.push_back( { CurrentStart, CurrentEnd } );

        return result;
    }
};
23200