There are 30 persons, 15 are believers, 15 are non-believers, they plan to travel.
A bus can only carry 15 of them, the rest have to be left behind.
Someone suggests they stand in a circle and count, beginning from him, every time one counts to 9, he has to stay and quite counting.
Finally all the 15 believers will travel, all 15 non-believers have to stay.
The question: how do they stand in the line?
有30个人， 15个信徒， 15个非信徒， 他们计划去旅行。 但是大巴只能装下15个人， 剩下的人没法去， 得留下。
有人提议站成一个圆圈， 从他起， 轮流数数， 每个数到9的人就留下， 退出圆圈， 不再参与数数。
到最后剩下的15个人， 发现都是信徒， 那么问题是， 这30个人是如何站成一个圈的。
import java.util.ArrayList;
public class Believer {
public static void main(String[] args) {
ArrayList list = new ArrayList<>();
for (int i = 1; i <= 30; i ++) {
list.add(true);
}
/*
true means believer
false means nonBeliever
*/
int remaining = 15; // remaining nonBeliever
int index = 0; // the index of the list, should no be greater than 29
int count = 0; // the number of the count, when count is 9, someone has to stay
while (remaining > 0) { // when there are still non-believers
if (list.get(index)) { // when counts to a non-believer, set to false, so the next round will ignore this element
count ++;
if (count == 9) {
list.set(index, false); // this is a non-believer
remaining --;
count = 0;
}
}
index ++;
if (index == 30) {
index = 0;
}
}
System.out.println(list);
}
}
[true, true, true, true, false, false, false, false, false, true, true, false, true, true, true, false, true, false, false, true, true, false, false, false, true, false, false, true, true, false].
def main():
circle = [True] * 30
remaining = 15
count = 0
index = 0
while remaining > 0:
if circle[index]:
count = count + 1
if count == 9:
circle[index] = False
count = 0
remaining = remaining - 1
index = index + 1
if index == 30:
index = 0
print(circle)
if __name__ == "__main__":
main()
[True, True, True, True, False, False, False, False, False, True, True, False, True, True, True, False, True, False, False, True, True, False, False, False, True, False, False, True, True, False]