<p>You are given a 2D array of integers <code>envelopes</code> where <code>envelopes[i] = [w<sub>i</sub>, h<sub>i</sub>]</code> represents the width and the height of an envelope.</p>

<p>One envelope can fit into another if and only if both the width and height of one envelope are greater than the other envelope&#39;s width and height.</p>

<p>Return <em>the maximum number of envelopes you can Russian doll (i.e., put one inside the other)</em>.</p>

<p><strong>Note:</strong> You cannot rotate an envelope.</p>

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

<pre>
<strong>Input:</strong> envelopes = [[5,4],[6,4],[6,7],[2,3]]
<strong>Output:</strong> 3
<strong>Explanation:</strong> The maximum number of envelopes you can Russian doll is <code>3</code> ([2,3] =&gt; [5,4] =&gt; [6,7]).
</pre>

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

<pre>
<strong>Input:</strong> envelopes = [[1,1],[1,1],[1,1]]
<strong>Output:</strong> 1
</pre>

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

<ul>
	<li><code>1 &lt;= envelopes.length &lt;= 10<sup>5</sup></code></li>
	<li><code>envelopes[i].length == 2</code></li>
	<li><code>1 &lt;= w<sub>i</sub>, h<sub>i</sub> &lt;= 10<sup>5</sup></code></li>
</ul>

class Solution {
public:

    int solve(vector<int> store, int n){
        if(n == 0) return 0;
vector<int> temp;
temp.push_back(store[0]);

for(int i = 1;i < n;i++){
    if(store[i] > temp.back()){
        temp.push_back(store[i]);
    }
    else{
        int index = lower_bound(temp.begin(), temp.end(), store[i]) - temp.begin();
        temp[index] = store[i];
    }
}
return temp.size();
    }

    int maxEnvelopes(vector<vector<int>>& envelopes) {
        // sort(envelopes.begin(), envelopes.end());
        vector<int> store;

        map<int, vector<int>> mp;

        for(auto i:envelopes){
            mp[i[0]].push_back(i[1]);
        }

        for(auto i:mp){
            if(i.second.size() > 1){
                sort(i.second.begin(), i.second.end(), greater<int>());
            }
                for(auto j:i.second){
                    store.push_back(j);
                }          
        }
        int n = store.size();
        return solve(store, n);
    
    }
};
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