poj 3295

写完代码发现WA，无奈之下看了讨论区中的测试数据，觉得自己弱爆了！没理解到底什么是WFF，太急于写代码了！

先把错误代码贴出来，提醒我以后一定把题目审清楚再做题！

#include <iostream>
#include <stack>
#include <stdlib.h>
#include <stdio.h>
#include <string>

using namespace std;

int p,q,r,s,t;

int trans(char tmp)
{
if(tmp == '0')
return 0;
else if(tmp == '1')
return 1;
else if(tmp == 'p')
return p;
else if(tmp == 'q')
return q;
else if(tmp == 'r')
return r;
else if(tmp == 's')
return s;
else if(tmp == 't')
return t;
}

char transR(int tmp)
{
if(tmp == 0)
return '0';
else if(tmp == 1)
return '1';
}

int main()
{
freopen("in.txt","r",stdin); //输入重定向，输入数据将从in.txt文件中读取
freopen("out.txt","w",stdout); //输出重定向，输出数据将保存在out.txt文件中

string line;
while(cin >> line)
{
if(line.length() == 1 && line[0] == '0')
break;

int flag = 1;
string origin = line;

if(line.length() == 1)
flag = 0;
for(int i = 0;i < 32;++i)
{
t = i & 1;
s = (i >> 1) & 1;
r = (i >> 2) & 1;
q = (i >> 3) & 1;
p = (i >> 4) & 1;

line = origin;
int nowSite = line.length() - 1;
while(nowSite > 0)
{
if(line[nowSite - 1] == 'N')
{
line[nowSite - 1] = transR(!trans(line[nowSite]));
nowSite--;
}
else
{
int tmp1,tmp2;
tmp1 = trans(line[nowSite - 1]);
tmp2 = trans(line[nowSite]);

if(line[nowSite - 2] == 'K')
{
line[nowSite - 2] = transR(tmp1 & tmp2);
}
else if(line[nowSite - 2] == 'A')
{
line[nowSite - 2] = transR(tmp1 | tmp2);
}
else if(line[nowSite - 2] == 'C')
{
line[nowSite - 2] = transR(!tmp1 | tmp2);
}
else if(line[nowSite - 2] == 'E')
{
if(tmp1 == tmp2)
line[nowSite - 2] = '1';
else
line[nowSite - 2] = '0';
}
nowSite -=2;
}
}
if(line[0] == '0')
{
flag = 0;
//printf("%d\n",p);
break;
}
}
if(flag)
printf("tautology\n");
else
printf("not\n");
}
return 0;
}

之后是两份网上转来的优秀的值得学习的代码，一份是用递归做的，另一份是用表达式求值做的。这个题可以算式表达式求值的变种。

#include <iostream>
using namespace std;
char str[101];
int pos;
bool judge( char str[], int value )
{
pos++;
switch ( str[pos] )
{
case 'p': return value&1;
case 'q': return (value>>1)&1;
case 'r': return (value>>2)&1;
case 's': return (value>>3)&1;
case 't': return (value>>4)&1;
case 'K': return judge(str,value)&judge(str,value);
case 'A': return judge(str,value)|judge(str,value);
case 'N': return !judge(str,value);
case 'C': return (!judge(str,value))|judge(str,value);
case 'E': return judge(str,value)==judge(str,value);
default:;
}
}
int main()
{
bool mark;
while ( cin >> str && str[0] != '0' )
{
mark = true;
for ( int i = 0; i < 32; i++ )
{
pos = -1;
if ( !judge(str,i) ) {
mark = false; break;
}
}
if ( mark ) cout << "tautology" << endl;
else cout << "not" << endl;
}
return 0;
}

代码2：

#include <iostream>
using namespace std;
int Nth_Char;
char str[101];
bool step ( char str[101], int logicValue )
{
Nth_Char++;
switch ( str[Nth_Char] )
{
case 'p': return logicValue & 1;
case 'q': return ( logicValue >> 1 ) & 1;
case 'r': return ( logicValue >> 2 ) & 1;
case 's': return ( logicValue >> 3 ) & 1;
case 't': return ( logicValue >> 4 ) & 1;
case 'N': return !step ( str, logicValue );
case 'K': return step ( str, logicValue ) & step ( str, logicValue );
case 'A': return step ( str, logicValue ) | step ( str, logicValue );
case 'C': return !step (str, logicValue ) | step ( str, logicValue );
case 'E': return step ( str, logicValue ) == step ( str, logicValue );
default:;
}
}
bool judge ( char str[101] )
{
for ( int i = 0; i < 32; i++ )
{
Nth_Char = -1;
if ( !step ( str, i ) )
return false;
}
return true;
}
int main()
{
while ( cin >> str && str[0] != '0' )
{
if ( judge ( str ) )
cout << "tautology" << endl;
else
cout << "not" << endl;
}
return 0;
}

给一个布尔表达式，判断是不是恒真。
我是枚举然后用栈做的，判断栈顶俩元素，是布尔变量就直接算，不是就接着往栈里扔。
p.s.这让我想起了本学期那节逻辑课……因为样例就是p | ( !p )是恒真表达式…………
/*
ID: SummerDAway
PROG: 3295
LANG: C++
OJ: POJ.ORG
*/
#include <cstdlib>
#include <cctype>
#include <cstring>
#include <cstdio>
#include <cmath>
#include <algorithm>
#include <vector>
#include <string>
#include <iostream>
#include <sstream>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <fstream>
#include <numeric>
#include <iomanip>
#include <bitset>
#include <list>
#include <stdexcept>
#include <functional>
#include <utility>
#include <ctime>
using namespace std ;

char a[200] ;
map<char,int> f ;
int top ;
char Stack[200] ;

char Trans( bool x ) {
if ( x )    return '1' ;
else return '0' ;
}

void calc( char a , char x , char y ) {
top -= 3 ;
if ( a == 'K' )    Stack[top++] = Trans( f[x] & f[y] ) ;
if ( a == 'A' )    Stack[top++] = Trans( f[x] | f[y] ) ;
if ( a == 'C' )    Stack[top++] = Trans( (!f[x]) | f[y] ) ;
if ( a == 'E' )    Stack[top++] = Trans( !( f[x] ^ f[y] ) ) ;
return ;
}

bool judge( ) {
int len = strlen( a ) ;
for ( int i = 0 ; i < len ; i++ ) {
Stack[top++] = a[i] ;
bool flag = false ;
while ( top > 1 && !flag ) {
flag = true ;
char x = Stack[top-1] ;
char y = Stack[top-2] ;
if ( ( f[x] >= 0 && f[y] >= 0 ) ) {
calc( Stack[top-3] , y , x ) ;
flag = false ;
}
if ( f[x] >= 0 && y == 'N' ) {
top -= 2 ;
Stack[top++] = Trans( !f[x] ) ;
flag = false ;
}
}
}
if ( Stack[0] == '1' ) return true ;
else return false ;
}

int main() {
freopen( "3295.in" , "r" , stdin ) ;
freopen( "3295.out" , "w" , stdout ) ;
gets( a ) ;
while ( a[0] != '0' ) {
f['1'] = 1 , f['0'] = 0 ;
f['A'] = -1 , f['K'] = -1 , f['C'] = -1 , f['E'] = -1 , f['N'] = -1 ;
bool flag = true ;
for ( int t = 0 ; t < 2 ; t++ )
for ( int b = 0 ; b < 2 ; b++ )
for ( int c = 0 ; c < 2 ; c++ )
for ( int d = 0 ; d < 2 ; d++ )
for ( int e = 0 ; e < 2 ; e++ ) {
f['p'] = t , f['q'] = b , f['r'] = c , f['s'] = d , f['t'] = e ;
top = 0 ;
if ( !judge() )    {
flag = false ;
}
}
if ( flag ) printf( "tautology\n" ) ;
else printf( "not\n" ) ;
gets( a ) ;
}
return 0 ;
}