ISBN13 check digit: Difference between revisions
Added C
(→{{header|REXX}}: added the REXX computer programming language for this task.) |
(Added C) |
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=={{header|C}}==
<lang c>#include <stdio.h>
int check_isbn13(const char *isbn) {
int ch = *isbn, count = 0, sum = 0;
/* check isbn contains 13 digits and calculate weighted sum */
for ( ; ch != 0; ch = *++isbn, ++count) {
/* skip hyphens or spaces */
if (ch == ' ' || ch == '-') {
--count;
continue;
}
if (ch < '0' || ch > '9') {
return 0;
}
if (count & 1) {
sum += 3 * (ch - '0');
} else {
sum += ch - '0';
}
}
if (count != 13) return 0;
return !(sum%10);
}
int main() {
int i;
const char* isbns[] = {"978-1734314502", "978-1734314509", "978-1788399081", "978-1788399083"};
for (i = 0; i < 4; ++i) {
printf("%s: %s\n", isbns[i], check_isbn13(isbns[i]) ? "good" : "bad");
}
return 0;
}</lang>
{{out}}
<pre>
978-1734314502: good
978-1734314509: bad
978-1788399081: good
978-1788399083: bad
</pre>
=={{header|Go}}==
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