TAUT - Tautology
Write a program that checks if the given logical expression is a tautology. The logical expression is a tautology if it is always true, regardless of logical value of its variables.
Input
On the first line there is the number of expressions to check (at most 35). The expression is in a prefix notation, that means that operator precedes its arguments. The following logical operators will be used:
C - and D - or I - implies E - if, and only if N - not
The variables will be lowercase letters (a-z). There will be no more than 16 different letters in the expression. The length of the expression will not exceed 111 characters.
Output
For each expression write one word: YES if it is a tautology, NO in other case.
Example
Sample input: 7 IIpqDpNp NCNpp Iaz NNNNNNNp IIqrIIpqIpr Ipp Ezz Sample output: YES YES NO NO YES YES YES
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kuszi:
2015-09-08 11:38:05
@Harish Vishwakarma reverse Polish notation = postfix (operator after operands), Polish notation = prefix (operator before operands). Last edit: 2015-09-08 11:38:22 |
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Harish Vishwakarma:
2012-12-16 23:12:24
By 'prefix' notation, does it actually mean 'reverse polish' notation? |
Added by: | Piotr Ćowiec |
Date: | 2004-07-25 |
Time limit: | 3.463s |
Source limit: | 50000B |
Memory limit: | 1536MB |
Cluster: | Cube (Intel G860) |
Languages: | All except: NODEJS PERL6 VB.NET |