README ¶ < Previous Next > 224. Basic Calculator (Hard) Implement a basic calculator to evaluate a simple expression string. The expression string may contain open ( and closing parentheses ), the plus + or minus sign -, non-negative integers and empty spaces . Example 1: Input: "1 + 1" Output: 2 Example 2: Input: " 2-1 + 2 " Output: 3 Example 3: Input: "(1+(4+5+2)-3)+(6+8)" Output: 23 Note: You may assume that the given expression is always valid. Do not use the eval built-in library function. Related Topics [Stack] [Math] Similar Questions Evaluate Reverse Polish Notation (Medium) Basic Calculator II (Medium) Different Ways to Add Parentheses (Medium) Expression Add Operators (Hard) Basic Calculator III (Hard) Expand ▾ Collapse ▴ Documentation ¶ There is no documentation for this package. Source Files ¶ View all Source files basic_calculator.go Click to show internal directories. Click to hide internal directories.