题目是这样的，有五个不同颜色的房间排成一排，每个房间里分别住着一个不同国籍的人，每个人都喝一种特定品牌的饮料，抽一种特定品牌的烟，养一种宠物。没有任意两个人的任意属性值是相同的。问：是谁在养鱼？ 下面是给出的15条线索。
- 英国人住在红色的房子里；
- 瑞典人养狗作为宠物；
- 丹麦人喝茶；
- 绿房子紧挨着白房子，在白房子的左边；
- 绿房子的主人喝咖啡；
- 抽Pall Mall牌香烟的人养鸟；
- 黄色房子里的人抽Dunhill牌香烟；
- 住在中间那个房子里的人喝牛奶；
- 挪威人住在第一个房子里面；
- 抽Blends牌香烟的人和养猫的人相邻；
- 养马的人和抽Dunhill牌香烟的人相邻；
- 抽BlueMaster牌香烟的人喝啤酒；
- 德国人抽Prince牌香烟；
- 挪威人和住在蓝房子的人相邻；
- 抽Blends牌香烟的人和喝矿泉水的人相邻。
求解思路：多维穷举遍历每个属性值组成的“人”，并用条件中的个体条件（条件中只包含了一个人）来筛选，将其加入对应房子的候选人列表中。然后对5个房子的候选人列表进行多重遍历，并用事关两个人的条件（比如条件10、11）进行筛选，而且选中的5个人的属性值不能重复，最后输出正确答案。代码如下：
import java.util.Vector;
public class Einstein {
static class Person {
final COLOR color;
final NATION nation;
final DRINK drink;
final PET pet;
final CIGARETTE cigarette;
final int index; //在几号房子
public Person(COLOR color, NATION nation, DRINK drink, PET pet, CIGARETTE cigarette, int index) {
this.color = color;
this.nation = nation;
this.drink = drink;
this.pet = pet;
this.cigarette = cigarette;
this.index = index;
}
@Override
public String toString() {
return "Person{" +
"color=" + color +
", nation=" + nation +
", drink=" + drink +
", pet=" + pet +
", cigarette=" + cigarette +
", index=" + index +
'}';
}
}
enum COLOR {Yellow, Blue, Red, Green, White}
enum NATION {Norway, Denmark, England, Germany, Sweden}
enum DRINK {Water, Tea, Milk, Coffee, Beer}
enum PET {Cat, Horse, Bird, Fish, Dog}
enum CIGARETTE {Dunhill, Blends, PallMall, Prince, BlueMaster}
boolean test1(final Person person) {
return (person.color == COLOR.Red && person.nation == NATION.England) ||
(person.color != COLOR.Red && person.nation != NATION.England);
}
boolean test2(final Person person) {
return (person.nation == NATION.Sweden && person.pet == PET.Dog) ||
(person.nation != NATION.Sweden && person.pet != PET.Dog);
}
boolean test3(final Person person) {
return (person.nation == NATION.Denmark && person.drink == DRINK.Tea) ||
(person.nation != NATION.Denmark && person.drink != DRINK.Tea);
}
boolean test5(final Person person) {
return (person.color == COLOR.Green && person.drink == DRINK.Coffee) ||
(person.color != COLOR.Green && person.drink != DRINK.Coffee);
}
boolean test6(final Person person) {
return (person.cigarette == CIGARETTE.PallMall && person.pet == PET.Bird) ||
(person.cigarette != CIGARETTE.PallMall && person.pet != PET.Bird);
}
boolean test7(final Person person) {
return (person.color == COLOR.Yellow && person.cigarette == CIGARETTE.Dunhill) ||
(person.color != COLOR.Yellow && person.cigarette != CIGARETTE.Dunhill);
}
boolean test8(final Person person) {
return (person.index == 2 && person.drink == DRINK.Milk) ||
(person.index != 2 && person.drink != DRINK.Milk);
}
boolean test9(final Person person) {
return (person.index == 0 && person.nation == NATION.Norway) ||
(person.index != 0 && person.nation != NATION.Norway);
}
boolean test12(final Person person) {
return (person.cigarette == CIGARETTE.BlueMaster && person.drink == DRINK.Beer) ||
(person.cigarette != CIGARETTE.BlueMaster && person.drink != DRINK.Beer);
}
boolean test13(final Person person) {
return (person.nation == NATION.Germany && person.cigarette == CIGARETTE.Prince) ||
(person.nation != NATION.Germany && person.cigarette != CIGARETTE.Prince);
}
boolean test14(final Person person) {
return (person.color == COLOR.Blue && person.index == 1) ||
(person.color != COLOR.Blue && person.index != 1);
}
private Vector<Person> house0 = new Vector<>();
private Vector<Person> house1 = new Vector<>();
private Vector<Person> house2 = new Vector<>();
private Vector<Person> house3 = new Vector<>();
private Vector<Person> house4 = new Vector<>();
public void search() {
//先构造满足个体条件的人，然后加入不同的房子里，再对房子里面的人进行循环
for (COLOR color : COLOR.values()) {
for (NATION nation : NATION.values()) {
for (DRINK drink : DRINK.values()) {
for (PET pet : PET.values()) {
for (CIGARETTE cigarette : CIGARETTE.values()) {
for (int index = 0; index < 5; index++) {
final Person person = new Person(color, nation, drink, pet, cigarette, index);
//如果这个人满足个体条件，则加入对应的房子
if (test1(person) && test2(person) && test3(person) && test5(person) && test6(person) &&
test7(person) && test8(person) && test9(person) && test12(person) &&
test13(person) && test14(person)) {
switch (person.index) {
case 0:
house0.add(person);
break;
case 1:
house1.add(person);
break;
case 2:
house2.add(person);
break;
case 3:
house3.add(person);
break;
case 4:
house4.add(person);
break;
}
}
}
}
}
}
}
}
//对5个房子里面的人进行循环
for (Person person0 : house0) {
for (Person person1 : house1) {
for (Person person2 : house2) {
for (Person person3 : house3) {
for (Person person4 : house4) {
final Person[] people = {person0, person1, person2, person3, person4};
if (test4(people) && test10(people) && test11(people) && test15(people) && isDistinct(people)) {
//找到了正确结果并输出
for (Person person : people) {
System.out.println(person);
}
}
}
}
}
}
}
}
//判断这组人是否有状态重复。不重复的情况下应该每种属性的值只有一个人有
private boolean isDistinct(final Person... people) {
boolean[] colors = new boolean[5];
boolean[] nations = new boolean[5];
boolean[] drinks = new boolean[5];
boolean[] pets = new boolean[5];
boolean[] cigarettes = new boolean[5];
for (int i = 0; i < 5; i++) {
colors[people[i].color.ordinal()] = true;
nations[people[i].nation.ordinal()] = true;
drinks[people[i].drink.ordinal()] = true;
pets[people[i].pet.ordinal()] = true;
cigarettes[people[i].cigarette.ordinal()] = true;
}
boolean result = true;
for (int i = 0; i < 5; i++) {
result &= (colors[i] && nations[i] && drinks[i] && pets[i] && cigarettes[i]);
}
return result;
}
private boolean test4(final Person... people) {
int green = 0;
int white = 0;
for (Person person : people) {
if (person.color == COLOR.Green) green = person.index;
if (person.color == COLOR.White) white = person.index;
}
return green + 1 == white;
}
private boolean test10(final Person... people) {
int blends = 0;
int cat = 0;
for (Person person : people) {
if (person.cigarette == CIGARETTE.Blends) blends = person.index;
if (person.pet == PET.Cat) cat = person.index;
}
return (blends + 1 == cat) || (blends - 1 == cat);
}
private boolean test11(final Person... people) {
int horse = 0;
int dunhill = 0;
for (Person person : people) {
if (person.cigarette == CIGARETTE.Dunhill) dunhill = person.index;
if (person.pet == PET.Horse) horse = person.index;
}
return (horse + 1 == dunhill) || (horse - 1 == dunhill);
}
private boolean test15(final Person... people) {
int blends = 0;
int water = 0;
for (Person person : people) {
if (person.cigarette == CIGARETTE.Blends) blends = person.index;
if (person.drink == DRINK.Water) water = person.index;
}
return (blends + 1 == water) || (blends - 1 == water);
}
public static void main(String[] args) {
new Einstein().search();
}
}注：喜欢的朋友可以点赞关注，一起学习进步。
