<p>Given an array of intervals <code>intervals</code> where <code>intervals[i] = [start<sub>i</sub>, end<sub>i</sub>]</code>, return <em>the minimum number of intervals you need to remove to make the rest of the intervals non-overlapping</em>.</p>

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

<pre>
<strong>Input:</strong> intervals = [[1,2],[2,3],[3,4],[1,3]]
<strong>Output:</strong> 1
<strong>Explanation:</strong> [1,3] can be removed and the rest of the intervals are non-overlapping.
</pre>

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

<pre>
<strong>Input:</strong> intervals = [[1,2],[1,2],[1,2]]
<strong>Output:</strong> 2
<strong>Explanation:</strong> You need to remove two [1,2] to make the rest of the intervals non-overlapping.
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> intervals = [[1,2],[2,3]]
<strong>Output:</strong> 0
<strong>Explanation:</strong> You don&#39;t need to remove any of the intervals since they&#39;re already non-overlapping.
</pre>

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

<ul>
	<li><code>1 &lt;= intervals.length &lt;= 10<sup>5</sup></code></li>
	<li><code>intervals[i].length == 2</code></li>
	<li><code>-5 * 10<sup>4</sup> &lt;= start<sub>i</sub> &lt; end<sub>i</sub> &lt;= 5 * 10<sup>4</sup></code></li>
</ul>

class Solution {
public:
    int f(vector<vector<int>>& v,int n,int index,int first,int second,unordered_map<int,int>& dp){
        if(index == n)return 0;
        if(dp.find(index) != dp.end())return dp[index];
            if(v[index][0] < second){
                first = 1 + f(v,n,index+1,first,min(second,v[index][1]),dp);
            }
            else first = f(v,n,index+1,v[index][0],v[index][1],dp);
            
        return dp[index] = min(first,INT_MAX-6);
    }
    int eraseOverlapIntervals(vector<vector<int>>& intervals) {
        sort(intervals.begin(),intervals.end());
        int n = intervals.size();
        if(n == 1)return 0;
        int first = intervals[0][0],second = intervals[0][1];
        unordered_map<int,int> dp;
        return f(intervals,n,1,first,second,dp);
    }
};
147375