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Q49.java
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Q49.java
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import java.util.HashSet;
import java.util.LinkedList;
import java.util.Queue;
import java.util.Set;
public class Q49 {
static final int N = 8;
static final int N2 = N * 2;
public static void main (String[] args) {
int[] mask = make_mask();
String str_end_pattern_1 = "", str_end_pattern_2 = "";
for (int i = 0; i < N2; i++) {
str_end_pattern_1 += i % 2 == 0 ? "1" : "0";
str_end_pattern_2 += i % 2 == 0 ? "0" : "1";
}
int end_pattern_1 = Integer.parseInt(str_end_pattern_1, 2);
int end_pattern_2 = Integer.parseInt(str_end_pattern_2, 2);
String left = "", right = "";
for (int i = 0; i < N; i++) {
left += "1";
right += "0";
}
int start = Integer.parseInt(left + right, 2);
Queue<Integer> q_cards = new LinkedList<>();
Queue<Integer> q_step = new LinkedList<>();
Set<Integer> set = new HashSet<>();
q_cards.add(start);
q_step.add(0);
set.add(start);
while (!q_cards.isEmpty()) {
int cards = q_cards.poll();
int step = q_step.poll();
if (cards == end_pattern_1 || cards == end_pattern_2) {
System.out.println(step);
break;
}
for (int i = 0; i < N2; i++) {
int next_cards = cards^mask[i];
if (set.contains(next_cards)) continue;
q_cards.add(next_cards);
q_step.add(step + 1);
set.add(next_cards);
}
}
}
static int[] make_mask () {
int[] ret = new int[N2];
String mask = "111";
while (mask.length() < N2) mask += "0";
for (int si = 0; si < N2; si++) {
ret[si] = Integer.parseInt(mask, 2);
char tail = mask.charAt(N2 - 1);
mask = tail + mask.substring(0, N2 - 1);
}
return ret;
}
static void debug_mask (int[] mask) {
System.out.print("[" + Integer.toBinaryString(mask[0]));
for (int i = 1; i < N2; i++)
System.out.print(", " + Integer.toBinaryString(mask[i]));
System.out.println("]");
}
}