brie, 10 months ago

This gave me the idea to do the same in C, but use the argument string itself as the stack to avoid any allocations. It could probably be further optimized.

<span style="color:#323232;">#include <stdio.h>
</span><span style="color:#323232;">
</span><span style="color:#323232;">int main(int argc, char **argv)
</span><span style="color:#323232;">{
</span><span style="color:#323232;">	char map[256] = { 0 };
</span><span style="color:#323232;">	map[')'] = '(';
</span><span style="color:#323232;">	map['}'] = '{';
</span><span style="color:#323232;">	map[']'] = '[';
</span><span style="color:#323232;">
</span><span style="color:#323232;">	while (--argc) {
</span><span style="color:#323232;">		char *top, *p, c;
</span><span style="color:#323232;">		top = p = *++argv;
</span><span style="color:#323232;">
</span><span style="color:#323232;">		while ((c = *p++)) {
</span><span style="color:#323232;">			if (top != *argv && map[(size_t)c] == top[-1]) {
</span><span style="color:#323232;">				top--;
</span><span style="color:#323232;">			} else {
</span><span style="color:#323232;">				*top++ = c;
</span><span style="color:#323232;">			}
</span><span style="color:#323232;">		}
</span><span style="color:#323232;">
</span><span style="color:#323232;">		*top = 0;
</span><span style="color:#323232;">
</span><span style="color:#323232;">		puts(*argv);
</span><span style="color:#323232;">	}
</span><span style="color:#323232;">}
</span>