// 1498. Number of Subsequences That Satisfy the Given Sum Condition #include "leetcode.h" /* * given an array of integers 'nums' and an integer 'target' * return the numbe of non-empty subsequences of 'nums' such * that the sum of the minimum and maximum element on it is * less or equal to 'target'. return modulo 10^9+7 */ int cmp(const void *a, const void *b) { return *(int *)a - *(int *)b; } int numSubseq(int *nums, int numsSize, int target) { qsort(nums, numsSize, sizeof(int), cmp); int ans = 0, l = 0, r = numsSize - 1, mod = 1e9 + 7; int *pows = (int *)malloc(numsSize * sizeof(int)); pows[0] = 1; for (int i = 1; i < numsSize; ++i) pows[i] = (pows[i - 1] << 1) % mod; while (l <= r) { if (nums[l] + nums[r] > target) { --r; continue; } ans = (ans + pows[r - l]) % mod; ++l; } free(pows); return ans; } int main() { int n1[] = {3, 5, 6, 7}; int n2[] = {3, 3, 6, 8}; int n3[] = {2, 3, 3, 4, 6, 7}; printf("%d\n", numSubseq(n1, ARRAY_SIZE(n1), 9)); // expect: 4 printf("%d\n", numSubseq(n2, ARRAY_SIZE(n2), 10)); // expect: 6 printf("%d\n", numSubseq(n3, ARRAY_SIZE(n3), 12)); // expect: 61 }