Question
Implement a basic calculator to evaluate a simple expression string.
The expression string contains only non-negative integers, +, -, *, / operators and empty spaces . The integer division should truncate toward zero.
You may assume that the given expression is always valid.
Some examples:
"3+2*2" = 7
" 3/2 " = 1
" 3+5 / 2 " = 5
Note: Do not use the eval built-in library function.
Quick Hints
- Use a
Stack - Do
*and/first - Push
+and-with correct sign for the number
Solution
Time complexity
O (n)
Space complexity
O (n) taken by stack in case if all operators are + or -