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// 1191. K-Concatenation Maximum Sum
#include "leetcode.h"
/*
* given an integer array 'arr' and an integer 'k', modify the array by
* repeating it 'k' times. for example, if 'arr = [1, 2]' and 'k = 3' then the
* modified array will be '[1, 2, 1, 2, 1, 2]'. return the maximum sub array sum
* in the modified array. note that the length of the sub array can be 0 and its
* sum in that case is 0. as the answer can be very large, return the answer
* modulo 1e9+7
*/
long long max_sum(int *arr, int arrSize) {
long long max = 0, sum = 0;
for (int i = 0; i < arrSize; i++) {
sum += arr[i];
max = sum > max ? sum : max;
if (sum < 0)
sum = 0;
}
return max;
}
int kConcatenationMaxSum(int *arr, int arrSize, int k) {
int mod = 1e9 + 7;
long long sum = 0;
for (int i = 0; i < arrSize; i++)
sum += arr[i];
if (k < 2)
return (int)(max_sum(arr, arrSize) % mod);
int *double_arr = (int *)malloc(arrSize * 2 * sizeof(int));
for (int i = 0; i < arrSize; i++) {
double_arr[i] = arr[i];
double_arr[i + arrSize] = arr[i];
}
if (sum < 0)
return (int)(max_sum(double_arr, arrSize * 2) % mod);
return (int)((max_sum(double_arr, arrSize * 2) + (k - 2) * sum) % mod);
}
int main() {
int a1[] = {1, 2}, a2[] = {1, -2, 1}, a3[] = {-1, -2};
printf("%d\n", kConcatenationMaxSum(a1, ARRAY_SIZE(a1), 3)); // expect: 9
printf("%d\n", kConcatenationMaxSum(a2, ARRAY_SIZE(a2), 5)); // expect: 2
printf("%d\n", kConcatenationMaxSum(a3, ARRAY_SIZE(a3), 7)); // expect: 0
}
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