qnikst.c

#define _GNU_SOURCE
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <stdio.h>

#define CHUNK_SIZE 40000000
#define LINES_CHUNK_SIZE 100000
#define BUF_SIZE 160000

void dump(char *buffer, int size) {
   while (size>0) {
     int w = write(1, buffer, size);
     buffer+=w;
     size-=w;
   }
}

static inline char * dumpstr(char *buffer, char *current, char *word) {
  int capacity = buffer+BUF_SIZE-current;
  while (*word) {
    if (capacity == 0) {
       dump(buffer, current - buffer);
       current = buffer;
       capacity = BUF_SIZE;
    }
    *current = *word;
    current++;
    word++;
    capacity--;
  }
  return current;
}

int main() {
	// INPUT reading
	char *buf = malloc(CHUNK_SIZE);
	int size = CHUNK_SIZE;
	{
	  char *s = buf;
	  int left = CHUNK_SIZE;
	  while(1){
	  	int n = read(0, s, left);
	  	if(n == 0) break;
	  	s += n; left -= n;
	  	if(left == 0) {
                   int tmp = size;
	           size += CHUNK_SIZE;
		   left = CHUNK_SIZE;
	  	   buf=realloc(buf, size);
		   s = buf + tmp;
	  	}
	  }
	  *s = '\n';
	}

	char **w = NULL;
	int k = 0;
	{
	  char *l_start = buf;
  	  while(1){
  		if (k % LINES_CHUNK_SIZE == 0) {
  		   w = realloc(w, k+LINES_CHUNK_SIZE);
  		}
  		char *l_end = memchr(l_start, '\n', buf+size-l_end);
  		if (l_end == NULL) break;
  		w[k] = l_start;
  		*l_end = '\0';
  		char *brk = rawmemchr(l_start, ' ');
  		l_start = l_end + 1;
  		if (*(l_end-1) == '\r') *(l_end-1) = '\0';
  		*brk = '\0';
  		w[k+1] = brk + 1;
  		k += 2;
  	  }
	}

	char out_buf[BUF_SIZE];
	char *s = out_buf;
	for(int i = 0; i < k; i+=2)
		for(int j = 1; j < k; j+=2){
			s=dumpstr(out_buf,s,w[i]);
			s=dumpstr(out_buf,s,w[j]);
			s=dumpstr(out_buf,s,"\n");
		}
	dump(out_buf, s - out_buf);
	return 0;
}