package Question10_3;
import java.io.*;
import java.util.*;
public class QuestionB {
public static int bitsize = 1048576; // 2^20 bits (2^17 bytes)
public static int blockNum = 4096; // 2^12
public static byte[] bitfield = new byte[bitsize/8];
public static int[] blocks = new int[blockNum];
public static void findOpenNumber() throws FileNotFoundException {
int starting = -1;
Scanner in = new Scanner (new FileReader ("Chapter 10/Question10_3/input_file_q10_3.txt"));
while (in.hasNextInt()) {
int n = in.nextInt();
blocks[n / (bitfield.length * 8)]++;
}
for (int i = 0; i < blocks.length; i++) {
if (blocks[i] < bitfield.length * 8){
/* if value < 2^20, then at least 1 number is missing in
* that section. */
starting = i * bitfield.length * 8;
break;
}
}
in = new Scanner(new FileReader("Chapter 10/Question10_3/input_file_q10_3.txt"));
while (in.hasNextInt()) {
int n = in.nextInt();
/* If the number is inside the block that�s missing
* numbers, we record it */
if (n >= starting && n < starting + bitfield.length * 8) {
bitfield [(n-starting) / 8] |= 1 << ((n - starting) % 8);
}
}
for (int i = 0 ; i < bitfield.length; i++) {
for (int j = 0; j < 8; j++) {
/* Retrieves the individual bits of each byte. When 0 bit
* is found, finds the corresponding value. */
if ((bitfield[i] & (1 << j)) == 0) {
System.out.println(i * 8 + j + starting);
return;
}
}
}
}
public static void main(String[] args) throws FileNotFoundException {
findOpenNumber();
}
}