Limbajul C. Exercitii clasice cu siruri de caractere. MyStrcmp si eliminarea asa-numitelor white-spaces

1. Clasicul MyStrcmp

Doua siruri de caractere sunt "egale" daca au exact aceleasi caractere dispuse in aceeasi ordine.

O functie testeaza aceasta "egalitate" si intoarce zero in caz ca se verifica egalitatea.

Daca sir1 < sir2, adica daca verificarea, pentru un caracter oarecare, incepand cu primul, a codurilor ASCII, satisface inegalitatea, functia intoarce -1.

In caz contrar, intoarce +1.

Codul si printscreen-ul:

#include <stdio.h>

int MyStrcmp(char *s1, char *s2);

void FeedString(char *s); // in loc de functiile predefinite gets si scanf

int main()

{

            char s1[31], s2[31];// vectori de max 30 de caractere + terminatorul de sir

            int check;

            puts("Introduceti primul sir, s1. Incheiati cu zero.");

            FeedString(s1);

            puts("Introduceti al doilea sir, s2. Incheiati cu zero.");

            FeedString(s2);

            check = MyStrcmp(s1, s2);

            if(!check) printf("\nSirurile sunt egale.\n");

            else if(check < 0) printf("\nSirul %s < %s.\n", s1, s2);

            else printf("\nSirul %s > %s.\n", s1, s2);

            return 0;

}

int MyStrcmp(char *s1, char *s2)

{

            int l1, l2, i;

            i = l1 = l2 = 0;

            //De fapt, se poate renunta la portiunea de cod

            //pentru calculul lungimii sirurilor si la

            //luarea deciziei pe baza compararii lungimilor.

            //Rezolvarea a fost scrisa astfel pentru a ilustra

            //prioritatile diferite ale operatorului de indexare

            //si a celui de incrementare postfix

            while(s1[l1++] != '\0');

            l1--;

            while(s2[l2++] != '\0');

            l2--;

            if(l1 != l2)

            {

                        for(; i < (l1 < l2? l2 : l1); i++)

                        {

                                    if(s1[i] == s2[i]) continue;

                                    else if(s1[i] < s2[i]) return -1;

                                    else return 1;

                        }

                       

            }

            else

            {

                        i = 0;

                        while(s1[i] == s2[i]) i++;

                        i;

                        if(i - 1 == l1) return 0;

                        else if(s1[i] < s2[i]) return -1;

                        else return 1;

            }                      

                       

}

void FeedString(char *s)

{

            int i = 0;

            char c = '\0';

            while((c = getchar()) != '0')

            {

                        s[i] = c;

                        if(i == 29)

                        {

                                    s[i + 1] = '\0';

                                    _flushall();

                                    break;

                        }

                        i++;

                        s[i] = '\0';

            }

            _flushall();

}

2. Clasicul program de eliminare a caracterelor white-space dintr-un sir.

Se scrie o functie de eliminare a unui caracter white-space, fie el spatiu (ASCII 32), tab (ASCII 9) sau new line ('\n'. Compilatorul va efectua translatia line feed + carriage return, coduri ASCII 10 si 13). 

Odata caracterul 'alb' eliminat, se invoca in mod convenabil, intr-o bucla, functia pana la elimitarea tuturor caracterelor white-space.

Codul si printscreen-ul:

#include <stdio.h>

void EliminWhite(char tab[], int n, int poz);

void FeedString(char *p);

int main()

{

            char tab[81];

    int i = 0, l = 0;

            puts("Introduceti un sir de max. 80 de caractere terminat prin 0.\nPoate contine whitespaces. Le vom elimina!\n");

            FeedString(tab);

            while(tab[l++] != '\0');

            l--;

            while(tab[i++] != '\0') if(tab[i - 1] == '\t' || tab [i - 1] == '\n' || tab[i - 1] == ' ') EliminWhite(tab, l, i - 1);

            printf("\nAm elimitat white-spaces si a rezultat sirul:\n\n%s\n", tab);

            return 0;

}

void EliminWhite(char tab[], int n, int poz)

{

            int i;

            for(i = poz; i < n; i++) tab[i] = tab[i + 1];

           

}

void FeedString(char *p)

{

            int i = 0;

            char c = '\0';

            while((c = getchar()) != '0')

            {

                        p[i] = c;

                        if(i == 80)

                        {

                                    p[i + 1] = '\0';

                                    _flushall();

                                    break;

                        }

                        p[i + 1] = '\0';

                        i++;

            }

            _flushall();

}