POJ 3295 Tautology

题意：逻辑运算题，最多有5个变量，依次枚举就可以AC了

k	A	N	C	E
a && b	a || b	!a	!a || b	a ==b

思路：之前是用递归写的，但是WA或是超时，郁闷。。。后来在网上参考了别人的代码，用栈一次AC。

 

 

 

10962407

NY_lv10

3295

Accepted

208K

16MS

C++

1648B

2012-10-27 20:08:57

 

#include <iostream>
#include <stack>
//#include <fstream>
#include <string>
using namespace std;

//ofstream out("1.txt");
string str;
stack<int> stk;
bool v[6];
bool tautology;

bool GetSult(/*int p*/)
{
    int a, b;
    for (int i = str.length()-1; i>=0; i--)
    {
        switch(str[i])
        {
        case 'K':
        {
            a = stk.top();
            stk.pop();
            b = stk.top();
            stk.pop();
            stk.push(a && b);
            //GetSult(p+1) && GetSult(p+2);
            break;
        }
        case 'A':
        {
            a = stk.top();
            stk.pop();
            b = stk.top();
            stk.pop();
            stk.push(a || b);
            break;
            //return GetSult(p+1) || GetSult(p+2);
        }
        case 'N':
        {
            a = stk.top();
            stk.pop();
            stk.push(!a);
            break;
            //return !GetSult(p+1);
        }
            //    return !v[str[p+1]-'p'];
        case 'C':
        {
            a = stk.top();
            stk.pop();
            b = stk.top();
            stk.pop();
            stk.push(!a || b);
            break;
            //return (!GetSult(p+1)) || GetSult(p+2);
        }
        case 'E':
        {
            a = stk.top();
            stk.pop();
            b = stk.top();
            stk.pop();
            stk.push(a == b);
            break;
            //return GetSult(p+1) == GetSult(p+2);
        }
        default:
            stk.push( v[str[i]-'p']);
        }
    }
    return stk.top();
}

int main()
{
    int i, j;
    while (cin>>str && str!="0")
    {
        while (!stk.empty())
            stk.pop();
        tautology = true;
        for (i=0; i<=31; i++)
        {
            for (j=0; j<5; j++)
                v[j] = (i>>j) % 2;
            
            if (!GetSult(/*0*/))        
            {
                tautology = false;
                goto L;
            }
        }
L:
        if (tautology)
        {
        //    out<<"tautology"<<endl;
            cout<<"tautology"<<endl;
        }
        else
        {
        //    out<<"not"<<endl;
            cout<<"not"<<endl;
        }
    }

    return 0;
}

 

#include <iostream>
#include <stack>
#include <fstream>
#include <string>
using namespace std;

ofstream out("1.txt");
string str;
stack<int> stk;
bool v[6];
bool tautology;

bool GetSult(int p)
{
    
    switch(str[p])
    {
    case 'K':
        return GetSult(p+1) && GetSult(p+2);
    case 'A':
        return GetSult(p+1) || GetSult(p+2);
    case 'N':
        return !GetSult(p+1);
        //    return !v[str[p+1]-'p'];
    case 'C':
         return (!GetSult(p+1)) || GetSult(p+2);
    case 'E':
        return GetSult(p+1) == GetSult(p+2);
    default:
        return v[str[p]-'p'];
    }
}

int main()
{
    int i, j;
    while (cin>>str && str!="0")
    {
        tautology = true;
        for (i=0; i<=31; i++)
        {
            for (j=0; j<5; j++)
                v[j] = (i>>j) % 2;
            
            if (!GetSult(0))        
            {
                tautology = false;
                goto L;
            }
        }
L:
        if (tautology)
        {
            out<<"tautology"<<endl;
            cout<<"tautology"<<endl;
        }
        else
        {
            out<<"not"<<endl;
            cout<<"not"<<endl;
        }
    }

    return 0;
}