// 1636. Sort Array by Increasing Frequency #include "leetcode.h" /* * given an array of integers 'nums', sort the array in increasing order based * on the frequency of the values. if multiple values have the same frequency, * sort them in decreasing order. return the sorted array. */ int cmp(const void *a, const void *b, void *cnt) { int *cnt_arr = (int *)cnt; int a_val = *(int *)a, b_val = *(int *)b; return cnt_arr[a_val + 100] == cnt_arr[b_val + 100] ? b_val - a_val : cnt_arr[a_val + 100] - cnt_arr[b_val + 100]; } int *frequencySort(int *nums, int numsSize, int *returnSize) { int cnt[201] = {0}; for (int i = 0; i < numsSize; ++i) ++cnt[nums[i] + 100]; qsort_r(nums, numsSize, sizeof(int), cmp, cnt); // requires _GNU_SOURCE return nums; } int main() { int n1[] = {1, 1, 2, 2, 2, 3}, n2[] = {2, 3, 1, 3, 2}, n3[] = {-1, 1, -6, 4, 5, -6, 1, 4, 1}, rs1, rs2, rs3; int *fs1 = frequencySort(n1, ARRAY_SIZE(n1), &rs1); int *fs2 = frequencySort(n2, ARRAY_SIZE(n2), &rs2); int *fs3 = frequencySort(n3, ARRAY_SIZE(n3), &rs3); for (int i = 0; i < rs1; i++) printf("%d ", fs1[i]); // expect: 3,1,1,2,2,2 printf("\n"); for (int i = 0; i < rs2; i++) printf("%d ", fs2[i]); // expect: 1,3,3,2,2 printf("\n"); for (int i = 0; i < rs3; i++) printf("%d ", fs3[i]); // expect: 5,-1,4,4,-6,-6,1,1,1 printf("\n"); free(fs1), free(fs2), free(fs3); }