Char comparison, ignoring the case sensitive

Question

The proposal is to create a program that compares n first positions of the two vectors and returns saying whether or not they are equal. So far so good, but I do not know how to ignore the case sensitive.

Here’s what I’ve done so far:

//Questão 7
#include <stdio.h>
#define MAX 5

int memcpy(char s1[], char s2[], int n);

int main()
{
    char s1_m[MAX]={'a', 'b', 'c', 'd', 'e'}, s2_m[MAX]={'a', 'b', 'c', 'D', 'E'};
    int n_m;

    printf("quantos caracteres serao verificados(max 5)\n> "); scanf("%d", &n_m); fflush(stdin);

    printf("os %d primeiros caracteres dos dois vetores %s iguais", n_m, memcpy(s1_m, s2_m, n_m)?"sao":"nao sao");
    return 0;
}

int memcpy(char s1[], char s2[], int n)
{
    int i, contador=0;

    for(i=0;i<n;i++)
    {
        if(s1[i]==s2[i])
            contador++;
        else
            break;
    }

    if(contador==n)
        i=1;
    else
        i=0;

    return i;
}

Answer 1

Just use the function tolower() to take everything tiny. I took advantage and improved some things, for example give a more meaningful name to the function and that does not overlap one existing in C:

#include <stdio.h>
#include <ctype.h>
#define MAX 5

int comparacao(char s1[], char s2[], int n) {
    int contador = 0;
    for (int i = 0; i < n; i++) {
        if (tolower(s1[i]) == tolower(s2[i])) contador++;
        else break;
    }
    return contador == n;
}

int main() {
    char s1_m[MAX] = {'a', 'b', 'c', 'd', 'e'}, s2_m[MAX] = {'a', 'b', 'c', 'D', 'E'};
    int n_m;
    printf("quantos caracteres serao verificados(max 5)\n> "); scanf("%d", &n_m);
    printf("os %d primeiros caracteres dos dois vetores %ssao iguais", n_m, comparacao(s1_m, s2_m, n_m) ? "" : "nao ");
}

Behold working in the ideone. And in the repl it.. Also put on the Github for future reference.

Can further simplify the comparison:

int i = 0;
for (; i < n && tolower(s1[i]) == tolower(s2[i]); i++);
return i == n;

Behold working in the ideone. And in the repl it.. Also put on the Github for future reference.

If you don’t want to use the ready the function is more or less this:

int tolower(int c) {
    if (c <= 'Z' && c >= 'A') return c + 32
    return c;
}