<p>Given an integer array <code>arr</code> and an integer <code>k</code>, modify the array by repeating it <code>k</code> times.</p>

<p>For example, if <code>arr = [1, 2]</code> and <code>k = 3 </code>then the modified array will be <code>[1, 2, 1, 2, 1, 2]</code>.</p>

<p>Return the maximum sub-array sum in the modified array. Note that the length of the sub-array can be <code>0</code> and its sum in that case is <code>0</code>.</p>

<p>As the answer can be very large, return the answer <strong>modulo</strong> <code>10<sup>9</sup> + 7</code>.</p>

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

<pre>
<strong>Input:</strong> arr = [1,2], k = 3
<strong>Output:</strong> 9
</pre>

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

<pre>
<strong>Input:</strong> arr = [1,-2,1], k = 5
<strong>Output:</strong> 2
</pre>

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

<pre>
<strong>Input:</strong> arr = [-1,-2], k = 7
<strong>Output:</strong> 0
</pre>

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

<ul>
	<li><code>1 &lt;= arr.length &lt;= 10<sup>5</sup></code></li>
	<li><code>1 &lt;= k &lt;= 10<sup>5</sup></code></li>
	<li><code>-10<sup>4</sup> &lt;= arr[i] &lt;= 10<sup>4</sup></code></li>
</ul>

class Solution {
public:
    int solve(vector<int>& arr) {
        int curr_sum = 0;
        int ans = 0;
        int n = arr.size();
        for(int i=0; i<n;i++){
            curr_sum = max(curr_sum+arr[i] , arr[i]);
            ans = max(ans , curr_sum);
        }
        return ans;
    }
    
    int kConcatenationMaxSum(vector<int>& arr, int k) {
        int n = arr.size();
        long long mod = 1e9+7;
        if(k==1)return  solve(arr);

        vector<int>vec;
        for(int i=0; i<2; i++){
            for(int j=0; j<n; j++){
                vec.push_back(arr[j]);
            }
        }
        int ans = solve(vec);
        // for(int i=0; i<vec.size(); i++)cout<<vec[i]<<" ";
        // cout<<ans;
        long long sum = 0;
        for(int i=0; i<n; i++){
            sum = sum + arr[i];
        }

        if(sum<0){
            return ans;
        }
        else{
            return ((long long)ans + (k-2)*sum)%mod;
        }

        return 0;
       
    }
};
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