爱因斯坦的思考题Java语言求解-白红宇

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
    
      house0 = new Vector<>();    private Vector
     
       house1 = new Vector<>();    private Vector
      
        house2 = new Vector<>();    private Vector
       
         house3 = new Vector<>();    private Vector
        
          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();    }}复制代码

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