LeetCode 1191. K-Concatenation Maximum Sum

class Solution {
public:
    int kConcatenationMaxSum(vector<int>& arr, int k) {
        int n = arr.size(), sum = arr[0], maxSum = arr[0];
        int64_t total = accumulate(arr.begin(), arr.end(), 0), mod = 1e9 + 7;
        for (int i = 1; i < n * min(k, 2); ++i) {
            if (sum > 0) sum += arr[i % n];
            else sum = arr[i % n];
            maxSum = max(maxSum, sum);
        }
        return max<int64_t>({0, maxSum, total * max(0, k - 2) + maxSum}) % mod;
    }
};