<p>Given two integer arrays&nbsp;<code>arr1</code> and <code>arr2</code>, return the minimum number of operations (possibly zero) needed&nbsp;to make <code>arr1</code> strictly increasing.</p>

<p>In one operation, you can choose two indices&nbsp;<code>0 &lt;=&nbsp;i &lt; arr1.length</code>&nbsp;and&nbsp;<code>0 &lt;= j &lt; arr2.length</code>&nbsp;and do the assignment&nbsp;<code>arr1[i] = arr2[j]</code>.</p>

<p>If there is no way to make&nbsp;<code>arr1</code>&nbsp;strictly increasing,&nbsp;return&nbsp;<code>-1</code>.</p>

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

<pre>
<strong>Input:</strong> arr1 = [1,5,3,6,7], arr2 = [1,3,2,4]
<strong>Output:</strong> 1
<strong>Explanation:</strong> Replace <code>5</code> with <code>2</code>, then <code>arr1 = [1, 2, 3, 6, 7]</code>.
</pre>

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

<pre>
<strong>Input:</strong> arr1 = [1,5,3,6,7], arr2 = [4,3,1]
<strong>Output:</strong> 2
<strong>Explanation:</strong> Replace <code>5</code> with <code>3</code> and then replace <code>3</code> with <code>4</code>. <code>arr1 = [1, 3, 4, 6, 7]</code>.
</pre>

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

<pre>
<strong>Input:</strong> arr1 = [1,5,3,6,7], arr2 = [1,6,3,3]
<strong>Output:</strong> -1
<strong>Explanation:</strong> You can&#39;t make <code>arr1</code> strictly increasing.</pre>

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

<ul>
	<li><code>1 &lt;= arr1.length, arr2.length &lt;= 2000</code></li>
	<li><code>0 &lt;= arr1[i], arr2[i] &lt;= 10^9</code></li>
</ul>

<p>&nbsp;</p>

struct hash_pair {
    template <class T1, class T2>
    size_t operator()(const pair<T1, T2>& p) const
    {
        auto hash1 = hash<T1>{}(p.first);
        auto hash2 = hash<T2>{}(p.second);
 
        if (hash1 != hash2) {
            return hash1 ^ hash2;              
        }
         
        // If hash1 == hash2, their XOR is zero.
          return hash1;
    }
};

class Solution {
public:
    int recur(vector<int> & arr1, vector<int> & arr2, int i, int prev, unordered_map<pair<int,int>,int,hash_pair>& dp, unordered_map<int,int> &greater){
        if (i == arr1.size()) return 0;

        if(dp.find({i,prev}) != dp.end()) return dp[{i,prev}];

        int j = greater[prev];

        int replace = 1e9;
        int notReplace = 1e9;

        if(j<arr2.size()) replace = 1+recur(arr1,arr2,i+1,arr2[j],dp,greater);
        if(arr1[i]>prev) notReplace = recur(arr1,arr2,i+1,arr1[i],dp,greater);

        return dp[{i,prev}] = min(replace,notReplace);
    }

    int makeArrayIncreasing(vector<int>& arr1, vector<int>& arr2) {
        int n = arr1.size();
        int m = arr2.size();
        sort(arr2.begin(),arr2.end());

        unordered_map<int,int> greater;
        for(auto num: arr1){
            int idx = upper_bound(arr2.begin(),arr2.end(),num)-arr2.begin();
            greater[num] = idx;
        }for(auto num: arr2){
            int idx = upper_bound(arr2.begin(),arr2.end(),num)-arr2.begin();
            greater[num] = idx;
        }
        
        unordered_map<pair<int,int>,int,hash_pair> dp;
        int res = recur(arr1,arr2,0,-1,dp,greater);
        return res >= 1e9? -1 : res;
    }
};
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