[POJ3295]Tautology
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[POJ3295]Tautology
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WFF ???N PROOF is a logic game played with dice. Each die has six faces representing some subset of the possible symbols K, A, N, C, E, p, q, r, s, t. A Well-formed formula (WFF) is any string of these symbols obeying the following rules:
- p, q, r, s, and t are WFFs
- if w is a WFF, Nw is a WFF
- if w and x are WFFs, Kwx, Awx, Cwx, and Ewx are WFFs.
The meaning of a WFF is defined as follows:
- p, q, r, s, and t are logical variables that may take on the value 0 (false) or 1 (true).
- K, A, N, C, E mean and, or, not, implies, and equals as defined in the truth table below.
w x | Kwx | Awx | Nw | Cwx | Ewx |
1 1 | 1 | 1 | 0 | 1 | 1 |
1 0 | 0 | 1 | 0 | 0 | 0 |
0 1 | 0 | 1 | 1 | 1 | 0 |
0 0 | 0 | 0 | 1 | 1 | 1 |
A tautology is a WFF that has value 1 (true) regardless of the values of its variables. For example, ApNp is a tautology because it is true regardless of the value of p. On the other hand, ApNq is not, because it has the value 0 for p=0, q=1.
You must determine whether or not a WFF is a tautology.
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Input consists of several test cases. Each test case is a single line containing a WFF with no more than 100 symbols. A line containing 0 follows the last case.
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For each test case, output a line containing tautology or not as appropriate.
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ApNp ApNq 0
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tautology
not
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?????? p, q, r, s, t ????????????????????????????????????????????????????????????????????????????????????tautology??????????????????not??????
#include <iostream> #include <cstdio> #include <algorithm> #include <cmath> #include <stack> #include <vector> #include <queue> #include <cstring> #include <string> #include <map> #include <set> using namespace std; #define maxn 110 #define maxal 300 char S[maxn]; int ord[maxal]; bool val[10]; struct Info { int p, v; Info() {} Info(int _, int __): p(_), v(__) {} } ; Info check(int l) { if(islower(S[l])) return Info(l + 1, val[ord[S[l]]]); if(S[l] == ???N???) { Info t; t = check(l + 1); return Info(t.p, t.v ^ 1); } if(S[l] == ???K???) { Info t, t2; t = check(l + 1); t2 = check(t.p); return Info(t2.p, t.v & t2.v); } if(S[l] == ???A???) { Info t, t2; t = check(l + 1); t2 = check(t.p); return Info(t2.p, t.v | t2.v); } if(S[l] == ???C???) { Info t, t2; t = check(l + 1); t2 = check(t.p); return Info(t2.p, (t.v && !t2.v) ? 0 : 1); } if(S[l] == ???E???) { Info t, t2; t = check(l + 1); t2 = check(t.p); return Info(t2.p, t.v == t2.v); } return Info(0, 0); } int main() { ord[???p???] = 0; ord[???q???] = 1; ord[???r???] = 2; ord[???s???] = 3; ord[???t???] = 4; while(scanf("%s", S + 1) == 1) { int all = (1 << 5) - 1, n = strlen(S + 1); if(n == 1 && S[1] == ???0???) break; bool ok = 1; for(int i = 0; i <= all; i++) { for(int j = 0; j < 5; j++) val[j] = (i >> j & 1); if(!check(1).v){ ok = 0; break; } } puts(ok ? "tautology" : "not"); } return 0; }
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