Uva592 Island of Logic

 

题意：神人鬼三个种族，神只说真话，鬼只说假话，人白天说真话，晚上说假话。根据对话内容区分种族和白天黑夜。  最多有A, B, C, D, E五个人

算法：枚举A, B, C, D, E的种族情况和白天黑夜的情况。每个人有可能是神人鬼，所以用两个bit表示，白天黑夜用1个bit表示。一共需要11 bits.

 

#include<iostream>
#include<cstdio>
#include<string>
using namespace std;

struct statement
{
    char a;//speaker
    char b;//object 等于状态的偏移量
    bool c;//not
    char d;
} p[50];

/*
A: I am [not] ( divine | human | evil | lying ).
A: X is [not] ( divine | human | evil | lying ).
A: It is ( day | night ).
*/
void get(statement &t)
{
    char c;
    cin >> c;
    t.a = c - 'A';
    cin >> c >> c;
    if (c == 'I')
    {
        cin.get(c);
        if (c == 't')//It is
            t.b = 5;//day|night偏移5
        else//I am
            t.b = t.a;
    }
    else
        t.b = c - 'A';//0-4对应 A-E  5对应day|night

    string s;
    cin >> s >> s;
    if (s == "not") t.c = true, cin >> s; else t.c = false;
    switch (s[0])
    {
    case 'd': t.d = 0; break;//day divine
    case 'e': t.d = 2; break;//evil
    case 'l': t.d = 3; break;//lying
    default: t.d = 1;//human night
    }
}


//human + night = 2
//evil + (day|night) >= 2
bool lying(short state, char who)
{
    return (state >> who*2 & 3) + (state >> 10 & 1) >= 2;
}

//this is too hard to understand
bool check(statement st, short s)
{
    return (st.d == 3 ? lying(s, st.b) : st.d == (s >> st.b + st.b & 3)) ^ st.c ^ lying(s, st.a);
}

//A-E 每个占2位; day,night 占1位
const int MAX_STATE=1<<11;
bool is_valid_state(int s)
{
    for(int i=0;i<5;i++)
        if((s>>i*2 & 3)==3)
            return false;
    return true;
}

//this is better then check function
//判断说话的人是否说谎话
//判断话的内容是否是真的
bool judge(statement st, short s)
{
    //if speaker is lying
    bool speaker=lying(s, st.a);

    //if statement is true
    bool object;

    //It is ( day | night ).
    if(st.b==5)
    {
        object = (s >> 10 & 1)==st.d;
        return speaker!=object;
    }

    //lying
    if(st.d==3)
    {
        if(st.c)
            object = !lying(s, st.b);
        else
            object = lying(s, st.b);

        return speaker!=object;
    }

    // X is [not] ( divine | human | evil )
    object = (s >> st.b*2 & 3)==st.d;

    return speaker!=object;
}

//如果状态矛盾，则置为 11b
void combine(short &a, short b)
{
    for (int i = 0; i < 6; ++i)
        if (a & (3 << i + i) ^ b & (3 << i + i))
            a |= (3 << i + i);
}

const char *s[] = { "divine", "human", "evil" };

int main()
{
#ifndef ONLINE_JUDGE
    freopen("./uva592.in", "r", stdin);
#endif
    int Kase=0;
    int n;
    //printf("%0X\n", MAX_STATE);
    while(cin>>n && n)
    {
        cout << "Conversation #" << ++Kase << endl;
        short a = -1;
        for(int i=0; i<n; i++) get(p[i]);
        for(int i=0; i<MAX_STATE; i++) if(is_valid_state(i))
        {
            bool b=true;
            for (int j=0; j<n; ++j) if (!check(p[j], i))
            {
                b = false;
                break;
            }
            if (!b) continue;
            if (a == -1) a = i; else combine(a, i);
        }
        if (a == -1) cout << "This is impossible." << endl;
        if (a == 0xFFF) cout << "No facts are deducible." << endl;
        for (int i = 0; i < 5; ++i)
        {
            int x = a>>i*2 & 3;
            if (x != 3) cout << char(i + 'A') << " is " << s[x] << "." << endl;
        }
        int x = a>>10 & 3;
        if (x != 3) cout << "It is " << (x ? "night." : "day.") << endl;
        cout << endl;
    }

    return 0;
}