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README.md | 2 years ago |
README.md
rpn
Instructions
Write a program which takes a string
containing an equation written in Reverse Polish Notation
(RPN). It should evaluate the equation, and print the result on the standard output followed by a newline ('\n'
).
Reverse Polish Notation
is a mathematical notation in which every operator follows all of its operands. In RPN, every operator encountered evaluates the previous 2 operands, and the result of this operation then becomes the first of the two operands for the subsequent operator. Operands and operators must be spaced by at least one space.
- If the
string
is not valid, or if there is not exactly one argument,Error
must be printed on the standard output followed by a newline. - If the
string
has extra spaces it is still considered valid.
The following operators must be implemented : +
, -
, *
, /
, and %
.
All the given operands must fit in a i64
.
Examples of formulas converted in RPN:
3 + 4 >> 3 4 +
((1 * 2) * 3) - 4 >> 1 2 * 3 * 4 - or 3 1 2 * * 4 -
50 * (5 - (10 / 9)) >> 5 10 9 / - 50 *
Here is how to evaluate a formula in RPN:
1 2 * 3 * 4 -
2 3 * 4 -
6 4 -
2
Or:
3 1 2 * * 4 -
3 2 * 4 -
6 4 -
2
For receiving arguments from the command line you should use something like:
fn main() {
let args: Vec<String> = std::env::args().collect();
rpn(&args[1]);
}
Usage
$ cargo run "1 2 * 3 * 4 +"
10
$ cargo run "1 2 3 4 +"
Error
$ cargo run ""
Error
$ cargo run " 1 3 * 2 -"
1
$ cargo run " 1 3 * ksd 2 -"
Error