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WHEN - When (You Believe) |
It's said: there can be miracles, when you believe. The following programming language shows the power of "when". It has a very simple (case insensitive) grammar, shown below:
PROGRAM := WHEN | PROGRAM WHEN WHEN := 'when ' EXPRESSION <ENTER> STATEMENTS 'end when' <ENTER> STATEMENTS := STATEMENT | STATEMENTS STATEMENT STATEMENT := PRINT | SET PRINT := 'print ' EXPRESSION_LIST <ENTER> SET := 'set ' ASSIGNMENT_LIST <ENTER> EXPRESSION_LIST := EXPRESSION | EXPRESSION_LIST ',' EXPRESSION ASSIGNMENT_LIST := ASSIGNMENT | ASSIGNMENT_LIST ',' ASSIGNMENT ASSIGNMENT := VARIABLE '=' EXPRESSION EXPRESSION := '(' EXPRESSION OP EXPRESSION ')' | VARIABLE | NUMBER OP := '<' | '+' | '-' | 'and' | 'or' | 'xor' VARIABLE := '$' NOT_DOLLAR_STRING '$' NUMBER := DIGIT | NUMBER DIGIT DIGIT := '0' | .. | '9' NOT_DOLLAR_STRING := any sequence of printable characters (including blanks) that does not contain a $ symbol.
In the above, any string enclosed in single quotes are to be treated literally. <ENTER> is the end of line.
In words, Spaces are allowed before or after any literal except inside a number. Spaces are allowed in variable names, and each non-empty sequence of spaces is treated as a single underscore, so the following refer to the same variable:
$Remote Switch#1$ $Remote_Switch#1$ $Remote switch#1$
All numbers appearing in the program will be integers between 0 and 1000000000, inclusive. All variable and literal values are integers between -1000000000 and 1000000000, inclusive. All variables are global and initially zero. The programs you will be tested on will never have an EXPRESSION that evaluates to a value outside of this range. The logical operators evaluate to 0 for false and 1 for true, and treat any nonzero value as true.
Running the program amounts to executing all the active when clauses until none are active. More specifically, the active list of when clauses is initially empty, then the following steps are repeated:
- In the order they appear in the program, the conditions of all when clauses that are not currently active are evaluated. If true, the clause is added to the end of the active list, with its first statement marked as "ready". Each active when clause has one "ready" statement.
- If the active list is empty after this step, the program terminates.
- The "ready" statement from the "current" when clause (initially the first clause in the active list) is executed.
- The statement marked as "ready" is advanced, removing the when clause from the active list if this is the last statement in the "current" when clause.
- The when clause marked as "current" is advanced, cycling to the beginning of the active list if the end is reached.
In other words, inactive when conditions are evaluated to determine if these clauses are added to the active list. Then one statement (set or print) is executed from the current active when clause. If this is the last statement in that clause, it is removed from the active list. One the next iteration, one statement is executed from the next active when clause, etc.
A set statement executes all the assignments concurrently, so that
set $x$=$y$,$y$=$x$
swaps the values of $x$ and $y$. The same variable cannot appear twice on the left hand part of the same set statement (so set $x$=1,$x$=2 is illegal).
A print statement evaluates and prints the given expressions in the output, separated by commas and followed by a new line. So
print 1,(2+3)
results in the line
1,5
in the output.
Input
The input consists of a single syntactically correct program. You may assume that the program will not execute more than 100000 set statements and 100000 print statements.
Output
Print the output produced by executing the given program. Both the input and output file will not exceed 100KB.
Example
Input: When ($Mr. Bill$<5) Set $mr._bill$=($mr. bill$+1),$Y$=($Y$+10) End When When ($mr. Bill$<10) Set $MR. BILL$=($mr. bill$+1) Print $mr. bill$,$Y$ End When Output: 3,20 6,40 7,40 8,40 9,40 10,40
Added by: | Fudan University Problem Setters |
Date: | 2009-02-17 |
Time limit: | 0.5s |
Source limit: | 11111B |
Memory limit: | 1536MB |
Cluster: | Cube (Intel G860) |
Languages: | All except: C99 ERL JS-RHINO NODEJS PERL6 VB.NET |
Resource: | Whitney Houston: When You Believe |
hide comments
2021-11-04 10:35:17 [Trichromatic] XilinX
The source limit has been relaxed from 6666B to 11111B. Last edit: 2021-11-04 10:35:31 |
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2020-06-09 19:50:34 Simes
AC with the slowest time by far, but at least it's AC. The source limit is a pain; C# is not the most terse of languages. It was a right pain shortening variable and class names, and removing indentation and comments to get under it. So unnecessary. |
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2016-05-25 13:49:49 Branfili
Cool problem, but source limit is ridiculous (for me). Also, AND, OR and XOR in WHEN are bitwise, it should be mentioned! (You say logical operators (as in plural) return 0 for false and 1 for true) |
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2016-05-11 02:02:24 Siarhei Kulik
Why Y=40? First, we execute one statement from each clause, thus getting 2,10 Then, we execute one statement from each clause again, getting 3,20 Then we execute one statement from each clause again and get 5,30 Then, we can't execute statement from the first clause because 5 is not < 5. So we execute the statement from the second clause and output 5,30. And so on.. Anyway, 5,30 should be outputted, and Y won't be changed more. Also, what is the priority of operations? Last edit: 2016-05-11 03:43:41 |
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2016-05-09 17:55:57 jkelava6
nvm Last edit: 2016-05-27 12:43:52 |
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2016-05-01 19:18:28
Is it possible to have a '\n' in a variable name? What characters are supposed to be printable ones? If variable name is 'a\n a' should I treat it as 'a_a' or 'a\n_a'? |
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2014-02-15 15:39:02 Grishnakh
Automata!!! Last edit: 2014-02-15 15:39:24 |