<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>

class Solution {
public:
    int makeArrayIncreasing(vector<int>& a, vector<int>& b) {
        int n = a.size(), m = b.size(), c = 1;
        sort(b.begin(), b.end());
        map<int, int> mp, mp1;
        for(int i = 0; i < n; i++)mp[a[i]] = c++;
        for(int i = 0; i < m; i++)mp[b[i]] = c++;
        for(auto el : mp)mp1[el.second] = el.first;
        vector<vector<int>> dp(n + 1, vector<int> (n + m + 1, -1));
        function<int(int i, int prev)> helper;
        helper = [&](int i, int prev){
            if(i == n)return 0;
            if(dp[i][prev] != -1)return dp[i][prev];
            if(prev == 0){
                int x = upper_bound(b.begin(), b.end(), prev) - b.begin();
                if(x != b.size())return dp[i][prev] = min(helper(i + 1, mp[a[i]]), 1 + helper(i + 1, mp[b[x]]));
                return dp[i][prev] = helper(i + 1, mp[a[i]]);
            }
            else{
                if(a[i] > mp1[prev]){
                    int x = upper_bound(b.begin(), b.end(), mp1[prev]) - b.begin();
                    if(x != b.size())return dp[i][prev] = min(helper(i + 1, mp[a[i]]), 1 + helper(i + 1, mp[b[x]]));
                    else return dp[i][prev] = helper(i + 1, mp[a[i]]);
                }
                else{
                    int x = upper_bound(b.begin(), b.end(), mp1[prev]) - b.begin();
                    if(x != b.size())return dp[i][prev] = 1 + helper(i + 1, mp[b[x]]);
                    else return dp[i][prev] = int(1e9);
                }
            }
        };
        int res = helper(0, 0);
        if(res >= 1e9)return -1;
        return res;
    }
};
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