[Informatik] Debug: a1.c
- From: Bennett Piater <bennett@xxxxxxxxxxx>
- To: cs-coop-uibk@xxxxxxxxxxxxx
- Date: Sat, 15 Nov 2014 14:22:58 +0100
Falls jemand Zeit haben sollte, einen Blick auf meinen Code zu werfen,
wäre ich sehr dankbar... Er scheint zu funktionnieren, aber eine meiner
eigenen Fehlermeldungen wird zu oft ausgegeben.
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
const int STR_MAX = 25;
bool check_palindrome(const char string[]);
int last_str_index(const char string[]);
void substring(const char string[], char* target, int begin, int end);
void max_palindrome(const char string[], char* target);
int main()
{
char string[STR_MAX];
printf("Enter a string without spaces: ");
scanf("%s", string);
bool palindrome = check_palindrome(string);
printf("Is this a palindrome? ");
printf("%s\n", palindrome ? "true" : "false");
char string2[15] = {0};
substring(string, string2, 2, 4);
printf("A substring from your string:\n");
printf("%s\n", string2);
char string3[STR_MAX];
printf("%lu\n", sizeof(string3));
max_palindrome(string, string3);
printf("The longest palindrome in your string:\n");
printf("%s\n", string3);
return EXIT_SUCCESS;
}
// Find the index of the last non-zero-item in a string
int last_str_index(const char string[])
{
// Iterate through the string
for (int i = 0; i < STR_MAX; ++i)
{
// Stop as soon as a zero is found
if (string[i] == 0)
return i-1;
}
// Satisfy GCC for a case that will never happen
return 0;
}
bool check_palindrome(const char string[])
{
bool result = true;
// Pre-calculate this for performance
int last = last_str_index(string);
// Reversely iterate through the characters of a string
for (int i = last; i >= 0; --i)
{
// Check if the item is equal to it's opposite within the
characters
if ((string[i] != string[last - i]))
{
result = false;
break;
}
}
return result;
}
void substring(const char string[], char* target, int begin, int end)
{
// Check if the source is readable
if ((begin > end) || (end > last_str_index(string)))
{
printf("These values won't work...\n");
return;
}
// Check if the target is long enough
else if((end - begin) > sizeof(target)) // use sizeof because it may
contain zeroes
// DEBUG - why does this return 8 when called from
max_palindrome? sizeof(target) should be 25!
{
printf("%lu ", sizeof(target));
printf("The target is too short!\n");
return;
}
int j = 0;
for (int i = begin; i <= end; ++i, ++j)
{
target[j] = string[i];
target[j+1] = 0; // Make the array a valid string
}
}
void max_palindrome(const char string[], char* target)
{
int new_len;
int old_len = 0;
// Pre-calculate this for performance
int length = last_str_index(string);
char tmp[length+1]; // This will always be long enough
for (int i = 0; i <= length; ++i) // i is the beginning,
{
for (int j = i; j <= length; ++j) // j is the end of the tested
substring
{
substring(string, tmp, i, j);
if (check_palindrome(tmp))
{
new_len = last_str_index(tmp);
// Check if this palindrome is longer than the
old one
if (new_len > old_len)
{
// It is, so make this the new result
old_len = new_len;
substring(string, target, i, j);
}
}
}
}
}
Other related posts:
