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Diffstat (limited to 'k_concatenation_max_sum.c')
-rw-r--r-- | k_concatenation_max_sum.c | 46 |
1 files changed, 46 insertions, 0 deletions
diff --git a/k_concatenation_max_sum.c b/k_concatenation_max_sum.c new file mode 100644 index 0000000..56002db --- /dev/null +++ b/k_concatenation_max_sum.c @@ -0,0 +1,46 @@ +// 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 +} |