The task in this problem is to evaluate a sequence of simple C expressions, but you need not know C to solve the problem! Each of the expressions will appear on a line by itself and will contain no more than 80 characters. The expressions to be evaluated will contain only simple integer variables and a limited set of operators; there will be no constants in the expressions. There are 26 variables which may appear in our simple expressions, namely those with the names a through z (lower-case letters only). At the beginning of evaluation of each expression, these 26 variables will have the integer values 1 through 26, respectively (that is, a = 1, b = 2, ...). Each variable will appear at most once in an expression and many variables may not be used at all.
The operators that may appear in expressions include the binary (two-operand)
+ and -, with the usual interpretation. Thus the expression
a + c
- d + b has the value 2 (computed as
1 + 3 - 4 + 2).
The only other operators that may appear in expressions are
--. These are unary (one-operand) operators, and may appear
before or after any variable. When the
++ operator appears
before a variable, that variable's value is incremented (by one) before
the variable's value is used in determining the value of the entire expression.
Thus the value of the expression
++ c - b is 2, with c being
incremented to 4 prior to evaluation the entire expression. When the
operator appears after a variable, that variable is incremented (again,
by one) after its value is used to determine the value of the entire expression.
Thus the value of the expression
c ++ - b is 1, but c is incremented
after the complete expression is evaluated; its value will still be 4. The
-- operator can also be used before or after a variable to
decrement (by one) the variable; its placement before or after the variable
has the same significance as for the
++ operator. Thus the
value of the expression
-- c + b -- has the value 4, with variables
b and c having the values 1 and 2 following the evaluation of the expression.
Here's another, more algorithmic, approach to explaining the
-- operators. We'll consider only the
Using this approach, evaluating the expression
++ a + b ++
is equivalent to computing
a = a + 1 (from step 1 of the algorithm)
expression = a + b (from step 3)
b = b + 1 (from
step 2) where expression would receive the value of the complete expression.
Your program is to read expressions, one per line, until a totally blank (or empty) line is read. Display each expression exactly as it was read, then display the value of the entire expression, and on separate lines, the value of each variable after the expression was evaluated. Do not display the value of variables that were not used in the expression. The samples shown below illustrate the desired output format.
Blanks are to be ignored in evaluating expressions, and you are assured
that ambiguous expressions like
a+++b (ambiguous because it
could be treated as
a++ + b or a + ++b) will not appear in
the input. Likewise,
-- operators will never
appear both before and after a single variable. Thus expressions like
will not be in the input data.
a + b b - z a+b--+c++ c+f--+--a f-- + c-- + d-++e
Expression: a + b value = 3 a = 1 b = 2 Expression: b - z value = -24 b = 2 z = 26 Expression: a+b--+c++ value = 6 a = 1 b = 1 c = 4 Expression: c+f--+--a value = 9 a = 0 c = 3 f = 5 Expression: f-- + c-- + d-++e value = 7 c = 2 d = 4 e = 6 f = 5