[Hacker Rank] Warmup: Time Conversion solved ✅. Better coverage + refactoring.

Author: Gonzalo Diaz

src/lib/exercises/src/hackerrank/warmup/time_conversion.c

@@ -1,5 +1,7 @@
 #include <exercises/hackerrank/warmup/time_conversion.h>
 
+#include <exercises/basic/common.h>
+
 /**
  * @link Problem definition [[docs/hackerrank/warmup/time_conversion.md]]
  */
@@ -9,43 +11,32 @@
 #include <string.h>
 
 char *HACKERRANK_WARMUP_firstN(const char *s, unsigned long n) {
-  unsigned long len = strlen(s);
-  if (n > len) {
-    return NULL;
-  }
-  if (n == 0) {
-    return NULL;
-  }
+  unsigned long len = MIN(strlen(s), n);
 
-  char *result = (char *)malloc((n + 1) * sizeof(char));
+  char *result = (char *)malloc((len + 1) * sizeof(char));
   if (result == NULL) {
     return NULL;
   }
 
-  strncpy(result, s, n);
+  strncpy(result, s, len);
 
-  result[n] = '\0';
+  result[len] = '\0';
 
   return result;
 }
 
 char *HACKERRANK_WARMUP_lastN(const char *s, unsigned long n) {
-  unsigned long len = strlen(s);
-  if (n > len) {
-    return NULL;
-  }
-  if (n == 0) {
-    return NULL;
-  }
+  unsigned long len_total = MIN(strlen(s), n);
+  unsigned long len_to_copy = MIN(len_total - n, 0l);
 
-  char *result = (char *)malloc((n + 1) * sizeof(char));
+  char *result = (char *)malloc((len_to_copy + 1) * sizeof(char));
   if (result == NULL) {
     return NULL;
   }
 
-  strncpy(result, s + len - n, n);
+  strncpy(result, s + len_total - len_to_copy, len_to_copy);
 
-  result[n] = '\0';
+  result[len_to_copy] = '\0';
 
   return result;
 }
@@ -77,7 +68,6 @@ char *HACKERRANK_WARMUP_timeConversion(const char *s) {
     free(hour_str);
     free(meridian);
     free(time_str);
-    free(endptr);
     return NULL;
   } else {
     printf("The integer value is: %ld\n", hour);

src/tests/unit/lib/hackerrank/warmup/time_conversion.test.cpp

@@ -34,9 +34,11 @@ TEST_CASE("time_conversion JSON Test Cases",
 
 TEST_CASE("time_conversion helper functions edge cases",
           "[hackerrank] [helper] [warmup]") {
-  CHECK(HACKERRANK_WARMUP_firstN("", 10) == nullptr);
-  CHECK(HACKERRANK_WARMUP_lastN("", 10) == nullptr);
+  CHECK(strcmp(HACKERRANK_WARMUP_firstN("", 10), "") == 0);
+  CHECK(strcmp(HACKERRANK_WARMUP_lastN("", 10), "") == 0);
 
-  CHECK(HACKERRANK_WARMUP_firstN("", 0) == nullptr);
-  CHECK(HACKERRANK_WARMUP_lastN("", 0) == nullptr);
+  CHECK(strcmp(HACKERRANK_WARMUP_firstN("", 0), "") == 0);
+  CHECK(strcmp(HACKERRANK_WARMUP_lastN("", 0), "") == 0);
+
+  CHECK(HACKERRANK_WARMUP_timeConversion("AA:BB:CCPM") == nullptr);
 }