Qsort array of strings in descending order

Question

To sort an array of strings in ascending order, I use:

int cmp(const void *p, const void *q) {
     char* const *pp = p;
     char* const *qq = q;
     return strcmp(*pp, *qq);
}

This will be then implemented into a qsort like so:

qsort(a, sizeof(a)(sizeof(a[0]), sizeof(a[0]), cmp);

How do you sort it in descending order?

wonglkd · Accepted Answer · 2013-11-27 20:02:33Z

7

One quick and easy way to do this is to multiply the result of strcmp() by -1 before returning it.

int cmp(const void *p, const void *q) {
     char* const *pp = p;
     char* const *qq = q;
     return -strcmp(*pp, *qq);
}

answered Nov 27, 2013 at 20:02

wonglkd

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2 Comments

Jonathan Leffler Over a year ago

Welcome to Stack Overflow. -1 * strcmp(…) is a long-winded way of writing -strcmp(…). Another option is strcmp(*qq, *pp), reversing the order of the arguments.

wonglkd Over a year ago

Thanks Jon, that's an excellent observation! I've amended the answer.

creichen · Accepted Answer · 2013-11-27 20:02:16Z

3

Just return the negative result (-strcmp(*pp, *qq)).

answered Nov 27, 2013 at 20:02

creichen

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1 Comment

Jonathan Leffler Over a year ago

Or use strcmp(*qq, *pp), reversing the order of the arguments.

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