Update README.md

csehammad · web-flow · commit f5762a3f5a86 · 2021-11-25T01:57:24.000+05:00
diff --git a/README.md b/README.md
@@ -40,5 +40,88 @@ Infix expression: 6 + (( 4 - (2 + 3 ) ) * 8 )
 Prefix expression: + 6 * - 4 + 2 3 8
 value: -2
 ``` 
+##### Variables
+So far we have only considered numbers as our operands for the prefix expression. For this test, we would like your function to also support variables withing the expression. 
 
+For example: 
+``` 
+expression: + 10 x 
+variables {"x":3}
+value: 13
+```
+##### Task
+
+Implement a function CalculateExpression(expression,variables)
+that takes as inputs:
+* expression, a string containing an expression in prefix notiation that might contain variables 
+* variables, a JSON objeect containing the values for each variable in the expression
+and returns: 
+* the result of the expression for the given values 
+* throw exception the expression is invalid or if the expression does not have any valid result
+
+The syntax supports 4 operators: +, -, *, and /. These are the standard artihmetic operators.
+* Note: / denotes integer division, that is / 7 2 evaluates to 3, not 3.5. 
+
+The only accepted numeric operands aer positive integers in base 10 (e.g 1,22, 85 are valid, -1,0x43, 0 are not valid).
+
+A valid variable name is any sequence of characters that doesn't include whitespaces(spaces,tabs, newlines, etc). 
+
+##### Examples
+
+```
+Expression: + 1 5
+variables: {}
+result: 6
+```
+
+```
+Expression: + 1 2 3
+variables: {}
+result: 6
+```
+
+```
+Expression: + 1
+variables: {}
+result: exception
+```
+
+```
+Expression: 9
+variables: {}
+result: 9
+```
+
+```
+Expression: * + 1 2 3
+variables: {}
+result: 9
+```
+
+Although, negative numeric operands are invalid in expression, intermediate and final results may be negative
+```
+Expression: + 6 * - 4 + 2 3 8 
+variables: {}
+result: -2
+```
+
+Operators and operrands must be seperated by one or more white spaces:
+```
+Expression: -+1 5 3
+variables: {}
+result: exception
+```
+ 
+```
+Expression: +1       2
+variables: {}
+result: 3
+```
+Expression containing variables:
+
+```
+Expression: * + 2 x y
+variables: {"x":1,"y":3}
+result: 9
+```
 
