diff options
Diffstat (limited to 'closest_prime_num_range.c')
-rw-r--r-- | closest_prime_num_range.c | 61 |
1 files changed, 61 insertions, 0 deletions
diff --git a/closest_prime_num_range.c b/closest_prime_num_range.c new file mode 100644 index 0000000..673ab00 --- /dev/null +++ b/closest_prime_num_range.c @@ -0,0 +1,61 @@ +// 2523. Closest Prime Numbers in Range +#include "leetcode.h" + +/* + * given two positive integers 'left' and 'right', find the two integers 'num1' + * and 'num2' such that 'left <= num1 < num2 <= right', both 'num1' and 'num2' + * are prime numbers, and 'num2 - num1' is the minimum amongst all other pairs + * satisfying the above conditions. return the positive integer array 'ans = + * [nums1, nums2]'. if there are multiple pairs satisfying these conditions, + * return the one with the smallest 'num1' value. if no such numbers exist, + * return '[-1, -1]'. + */ + +int *closestPrimes(int left, int right, int *returnSize) { + int *ans = (int *)malloc(2 * sizeof(int)); + *returnSize = 2; + ans[0] = -1; + ans[1] = -1; + + bool *sieve = (bool *)malloc((right + 1) * sizeof(bool)); + memset(sieve, true, (right + 1) * sizeof(bool)); + sieve[0] = sieve[1] = false; + for (int i = 2; i * i <= right; i++) + if (sieve[i]) + for (int j = i * i; j <= right; j += i) + sieve[j] = false; + int *prime = (int *)malloc((right - left + 1) * sizeof(int)); + int idx = 0; + for (int i = left; i <= right; i++) + if (sieve[i]) + prime[idx++] = i; + free(sieve); + if (idx < 2) { + free(prime); + return ans; + } + int min = INT_MAX; + for (int i = 1; i < idx; i++) { + int diff = prime[i] - prime[i - 1]; + if (min > diff) { + min = diff; + ans[0] = prime[i - 1]; + ans[1] = prime[i]; + } + } + free(prime); + return ans; +} + +int main() { + int rs1, *cp1 = closestPrimes(10, 19, &rs1); + int rs2, *cp2 = closestPrimes(4, 6, &rs2); + for (int i = 0; i < rs1; i++) + printf("%d ", cp1[i]); // expect: 11 13 + printf("\n"); + for (int i = 0; i < rs2; i++) + printf("%d ", cp2[i]); // expect: -1 -1 + printf("\n"); + free(cp1); + free(cp2); +} |