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-rw-r--r--find_palindrome_fixed_length.c45
1 files changed, 45 insertions, 0 deletions
diff --git a/find_palindrome_fixed_length.c b/find_palindrome_fixed_length.c
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+// 2217. Find Palindrome With Fixed Length
+#include "leetcode.h"
+
+/*
+ * given an integer array 'queries' and a positive integer 'intLength', return
+ * an array 'ans' where 'ans[i]' is either the 'queries[i]'th smallest positive
+ * palindreom of length 'intLength' or -1 if no such palindrome exists.
+ */
+
+long long reverse(int num, int n) {
+ long long res = 0;
+ if (n % 2)
+ num /= 10;
+ while (num) {
+ res = res * 10 + num % 10;
+ num /= 10;
+ }
+ return res;
+}
+
+long long *kthPalindrome(int *queries, int queriesSize, int intLength,
+ int *returnSize) {
+ long long *ans = (long long *)malloc(queriesSize * sizeof(long long));
+ *returnSize = queriesSize;
+ int n = (intLength + 1) / 2, min = pow(10, n - 1), max = pow(10, n) - 1,
+ mul = pow(10, n - intLength % 2);
+ for (int i = 0; i < queriesSize; i++)
+ ans[i] = min + queries[i] - 1 > max
+ ? -1
+ : (long long)(min + queries[i] - 1) * mul +
+ reverse(min + queries[i] - 1, intLength);
+ return ans;
+}
+
+int main() {
+ int q1[] = {1, 2, 3, 4, 5, 90}, q2[] = {2, 4, 6}, rs1, rs2;
+ long long *kp1 = kthPalindrome(q1, ARRAY_SIZE(q1), 3, &rs1);
+ long long *kp2 = kthPalindrome(q2, ARRAY_SIZE(q2), 4, &rs2);
+ for (int i = 0; i < rs1; i++)
+ printf("%lld ", kp1[i]); // expect: 101,111,121,131,141,999
+ printf("\n");
+ for (int i = 0; i < rs2; i++)
+ printf("%lld ", kp2[i]); // expect: 1111,1331,1551
+ printf("\n");
+}