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Rooted by: String Remover
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  • Algorithms
    Strings
    Description

    The hack has been banished.

     Code 
    #include <stdlib.h>
#include <string.h>

/*
  Heap allocate the string and return it.
*/

char* remove_string(const char *input, const int n)
{
  if (n <= 0 || input == NULL) return NULL;
  for (size_t i = 0, len = 0; i < (size_t)n; i++)
  {
    input += len;
    if ((len = strlen(input) + 1) == 1) return NULL;
  }  
  return strdup(input);
}
     Test Cases 
    #include <criterion/criterion.h>
#include <stdlib.h>
#include <string.h>

char* remove_string(const char *input, const int n);

void tester(const char *input, size_t index, const char *exp) 
{
  char *result = remove_string(input, index);
  if  (exp == NULL) cr_assert_eq(result, NULL, "Expected NULL but got %s.", result);
  else              cr_assert_str_eq(result, exp, "Expected '%s' but got '%s'.", exp, result);
  free(result);
}

Test(remove_string, should_pass_all_the_tests_provided) 
{
  tester("hello\0world\0", 1, "hello");
  tester("well\0done\0", 2, "done");
  tester("you\0are\0close\0", 3, "close");
  tester("you\0almost\0finished\0the\0kumite\0", 5, "kumite");
  tester("not\0the\0last\0string\0", 3, "last");
  tester("edge\0case\0", 0, NULL);
  tester("another\0edge\0case\0", 4, NULL);
}
    View Run Output
  • Code
    • #include <stdlib.h>
    • #include <string.h>
    • /*
    • Heap allocate the string and return it.
    • */
    • char* remove_string(const char *input, const int n)
    • {
    • if (n <= 0 || input == NULL) return NULL;
    • // This is a BIG hack, and I am unsure why it works since in an edge
    • // situation where "n" is greater than the number of '\0' in the string,
    • // the pointer will wander into unallocated memory.
    • for (int c = 1; c < n; input++, (*input == '\0' ? c++ && input++ : c));
    • char* res = strdup(input);
    • return *res == NULL ? NULL : res;
    • for (size_t i = 0, len = 0; i < (size_t)n; i++)
    • {
    • input += len;
    • if ((len = strlen(input) + 1) == 1) return NULL;
    • }
    • return strdup(input);
    • }