bitsort.c

#include<stdio.h>
#include<stdlib.h>

#define MAX_N 10000000

void set_bit(char *sort_bit, int value, int bit);
int get_bit(char *sort_bit, int value);

int main(void) {
  FILE *fp;
  char buf[10];
  char sort_bit[1250000];
  int i, value;

  if((fp = fopen("telno.txt", "r")) == NULL) {
    fprintf(stderr, "file open error!!\n");
    exit(EXIT_FAILURE);
  }

  for(i = 0; i < MAX_N; i++){
    set_bit(sort_bit, i, 0);
  }

  while(fgets(buf, sizeof(buf), fp) != NULL) {
    value = atoi(buf);
    set_bit(sort_bit, value, 1);
  }

  fclose(fp);

  if((fp = fopen("result.txt", "w")) == NULL) {
    fprintf(stderr, "file open error!!\n");
    exit(EXIT_FAILURE);
  }

  for(i = 0; i < MAX_N; i++) {
    if(get_bit(sort_bit, i) == 1) {
      fprintf(fp, "%07d\n", i);
    }
  }

  fclose(fp);

  return 0;
}

int get_bit(char *sort_bit, int value) {
  int index;
  int bit_index;
  char flag;

  index = value / 8;
  bit_index = value % 8;

  flag = 0x80 >> bit_index;

  if((sort_bit[index] & flag) == 0) {
    return 0;
  } else {
    return 1;
  }
}

void set_bit(char *sort_bit, int value, int bit) {

  int index;
  int bit_index;
  char flag;

  index = value / 8;
  bit_index = value % 8;

  if(bit == 1){
    flag = 0x80 >> bit_index;
  } else {
    switch(bit_index) {
      case 0:
        flag = 0x7f;
        break;
      case 1:
        flag = 0xbf;
        break;
      case 2:
        flag = 0xdf;
        break;
      case 3:
        flag = 0xef;
        break;
      case 4:
        flag = 0xf7;
        break;
      case 5:
        flag = 0xfb;
        break;
      case 6:
        flag = 0xfd;
        break;
      case 7:
        flag = 0xfe;
    }
  }

  if(bit == 1) {
    sort_bit[index] = sort_bit[index] | flag;
  } else {
    sort_bit[index] = sort_bit[index] & flag;
  }

}

flag = 0x80 >> bit_index
で、いけないですか？

おお、多分いけるね

いけた。