Basic Calculator
Explore how to implement a basic calculator that evaluates arithmetic expressions containing integers, plus and minus operators, and parentheses. Learn to use stacks effectively to parse and compute the result, handle unary minus, and manage operator precedence. This lesson helps you understand the stack-based approach to solving expression evaluation problems in coding interviews.
We'll cover the following...
Statement
Given a string containing an arithmetic expression, implement a basic calculator that evaluates the expression string. The expression string can contain integer numeric values and should be able to handle the “+” and “-” operators, as well as “()” parentheses.
Constraints:
Let s be the expression string. We can assume the following constraints:
-
s.length sconsists of digits, “+”, “-”, “(”, and “)”.srepresents a valid expression.- “+” is not used as a unary operation ( and are invalid).
- “-” could be used as a unary operation ( and are valid).
- There will be no two consecutive operators in the input.
- Every number and running calculation will fit in a signed 32-bit integer.
Examples
Understand the problem
Let’s take a moment to make sure you've correctly understood the problem. The quiz below helps you check if you're solving the correct problem:
Basic Calculator
What is the output if the following string is given as input?
(13 + 50) + (56 - 29 - (7 + 2))
-81
81
91
90
Figure it out!
We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.
Note: We'll evaluate the expression in the following sequence:
1) Convert consecutive digits into a single operand.
2) Handle "+", "-" operators.
3) Handle the "(" bracket.
4) Handle the ")" bracket.
Try it yourself
Implement your solution in the following coding playground:
int Calculator(string expression) {// Replace this placeholder return statement with your codereturn 0;}