As a solo warrior in OJ, I spent about nearly 50% of my time on tackling TLE - that is innumerous hours. I almost lost my courage to OJ.But thanks to this post: http://www.spoj.com/forum/viewtopic.php?f=3&t=7968. I didn't use all of the hints, but getchar_unlocked works like charms.
As advised, cin\cout is too slow. For example, my Dijkstra using cin\cout took 25+ seconds, but after using the below code piece to get ints:
#define gc getchar_unlocked int read_int() { char c = gc(); while(c<'0' || c>'9') c = gc(); int ret = 0; while(c>='0' && c<='9') { ret = 10 * ret + c - 48; c = gc(); } return ret; }
void print_fast(char *p) { fwrite_unlocked(p, 1, strlen(p), stdout); }
The same code ran only 11.34 seconds. Please note that, _unlocked API are not available on every platform - never mind, SPOJ has it.
And by the way, std::sync_with_stdio(false) gave segment error. I don't know why.
