// 368. Largest Divisible Subset #include "leetcode.h" /* * given a set of distinct positive integers 'nums', return the largest subset * 'answer' such that every pair '(ans[i], ans[j])' of elements in this subset * satifies 'ans[i] % ans[j] == 0' or 'ans[j] % ans[i] == 0'. if there are * multiple solutions, return any of them. */ int cmp(const void *a, const void *b) { return *(int *)a - *(int *)b; } int *largestDivisibleSubset(int *nums, int nums_size, int *return_size) { qsort(nums, nums_size, sizeof(int), cmp); int *idx = malloc(nums_size * sizeof(int)); int *cnt = malloc(nums_size * sizeof(int)); int max = 1, max_idx = 0, tmp; idx[0] = -1; cnt[0] = 1; for (int i = 1; i < nums_size; i++) { idx[i] = -1; cnt[i] = 1; for (int j = i - 1; j >= 0; j--) if (!(nums[i] % nums[j])) { tmp = cnt[j] + 1; if (tmp > cnt[i]) { cnt[i] = tmp; idx[i] = j; } } if (cnt[i] > max) { max = cnt[i]; max_idx = i; } } *return_size = max; int *ans = malloc(max * sizeof(int)); for (int i = max - 1; i >= 0; i--) { ans[i] = nums[max_idx]; max_idx = idx[max_idx]; } free(idx), free(cnt); return ans; } int main() { int n1[] = {1, 2, 3}, n2[] = {1, 2, 4, 8}; int rs1[] = {}, rs2[] = {}; int *lds1 = largestDivisibleSubset(n1, ARRAY_SIZE(n1), rs1); int *lds2 = largestDivisibleSubset(n2, ARRAY_SIZE(n2), rs2); for (int i = 0; i < 2; i++) printf("%d ", lds1[i]); // expect: 1 2 printf("\n"); for (int i = 0; i < 4; i++) printf("%d ", lds2[i]); // expect: 1 2 4 8 printf("\n"); free(lds1), free(lds2); }