<p>Given two integer arrays <code>nums1</code> and <code>nums2</code>, return <em>the maximum length of a subarray that appears in <strong>both</strong> arrays</em>.</p>

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

<pre>
<strong>Input:</strong> nums1 = [1,2,3,2,1], nums2 = [3,2,1,4,7]
<strong>Output:</strong> 3
<strong>Explanation:</strong> The repeated subarray with maximum length is [3,2,1].
</pre>

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

<pre>
<strong>Input:</strong> nums1 = [0,0,0,0,0], nums2 = [0,0,0,0,0]
<strong>Output:</strong> 5
<strong>Explanation:</strong> The repeated subarray with maximum length is [0,0,0,0,0].
</pre>

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

<ul>
	<li><code>1 &lt;= nums1.length, nums2.length &lt;= 1000</code></li>
	<li><code>0 &lt;= nums1[i], nums2[i] &lt;= 100</code></li>
</ul>

class Solution {
public:
    int findLength(vector<int>& nums1, vector<int>& nums2) {
        int low = 0;
        int high = min(nums1.size(), nums2.size());
        vector<long long> pow(max(nums1.size(), nums2.size()), 1);
        for(int i = 1; i<max(nums1.size(), nums2.size()); i++)
        {
            pow[i] = (pow[i-1] * base) % MOD;
        }
        while(low < high)
        {
            int mid = low + (high - low + 1)/2;
            if(checkLengthRabinKarp(nums1, nums2, pow, mid))
            {
                low = mid;    
            }
            else
            {
                high = mid-1;
            }
        }
        return low;
    }
    
    bool checkLengthRabinKarp(vector<int> &nums1, vector<int> &nums2, vector<long long> &pow, int length) {
        unordered_map<int,vector<int>> hash_map;
        unsigned long long hash = 0;
        for(int i = 0; i<length; i++)
        {
            hash = (hash * base + nums1[i]) % MOD;
        }
        hash_map[hash].push_back(0);
        for(int i = length; i < nums1.size(); i++)
        {
            // This is the main logic for rolling hash
            hash = (hash - (nums1[i - length] * pow[length-1] /*this is the inverse*/)%MOD + MOD) % MOD;
            hash = (hash * base + nums1[i]) % MOD;
            hash_map[hash].push_back(i);
        }
        hash = 0;
        for(int i = 0; i<length; i++)
        {
            hash = (hash * base + nums2[i]) % MOD;
        }
        if(hash_map.find(hash) != hash_map.end())
        {
            return true;
        }
        for(int i = length; i < nums2.size(); i++)
        {
            hash = (hash - (nums2[i - length] * pow[length-1] /*this is the inverse*/)%MOD + MOD) % MOD;
            hash = (hash * base + nums2[i]) % MOD;
            if(hash_map.find(hash) != hash_map.end())
            {
                return true;
            }
        }
        return false;
    }

private:
    const int base = 113;
    const int MOD = 1e9 + 7;
};
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