// 1497. Check If Array Pairs Are Divisible by k #include "leetcode.h" /* * given an array of integers 'arr' of even length 'n' and an integer 'k'. we * want to divide the array into exactly 'n / 2' pairs such that the sum of each * pair is divisible by 'k'. return 'true' if you can find a way to to that or * 'false' otherwise. */ bool canArrange(int *arr, int arrSize, int k) { int *freq = (int *)calloc(k, sizeof(int)); for (int i = 0; i < arrSize; i++) { int rem = ((arr[i] % k) + k) % k; freq[rem]++; } if (freq[0] % 2) return false; if (!(k % 2)) if (freq[k / 2] % 2) { free(freq); return false; } for (int r = 1; r <= k / 2; r++) if (r != k - r) if (freq[r] != freq[k - r]) return false; return true; } int main() { int a1[] = {1, 2, 3, 4, 5, 10, 6, 7, 8, 9}, a2[] = {1, 2, 3, 4, 5, 6}, a3[] = {1, 2, 3, 4, 5, 6}; printf("%d\n", canArrange(a1, ARRAY_SIZE(a1), 5)); // expect: 1 printf("%d\n", canArrange(a2, ARRAY_SIZE(a2), 7)); // expect: 1 printf("%d\n", canArrange(a3, ARRAY_SIZE(a3), 10)); // expect: 0 }