calculator in go

esa-kian · esa-kian · commit fed102b86a59 · 2024-02-05T14:20:06.000Z
diff --git a/src/hard/Calculator.go b/src/hard/Calculator.go
@@ -0,0 +1,137 @@
+package main
+
+import (
+	"fmt"
+	"strconv"
+)
+
+func Calculator(str string) int {
+	tokens := tokenize(str)
+	result, _ := evaluate(tokens)
+	return result
+}
+
+func tokenize(str string) []string {
+	var tokens []string
+
+	for i := 0; i < len(str); i++ {
+		switch {
+		case str[i] == ' ':
+			// Skip spaces
+			continue
+		case isDigit(str[i]):
+			// If it's a digit, extract the entire number
+			start := i
+			for i < len(str) && isDigit(str[i]) {
+				i++
+			}
+			tokens = append(tokens, str[start:i])
+			i--
+		default:
+			// If it's not a digit, add the operator or parenthesis as a token
+			tokens = append(tokens, string(str[i]))
+		}
+	}
+
+	return tokens
+}
+
+func isDigit(char byte) bool {
+	return char >= '0' && char <= '9'
+}
+
+func evaluate(tokens []string) (int, []string) {
+	var stack []int
+	var operators []string
+
+	for len(tokens) > 0 {
+		token := tokens[0]
+		tokens = tokens[1:]
+
+		switch token {
+		case "(":
+			// Recursively evaluate the expression inside the parentheses
+			result, remainingTokens := evaluate(tokens)
+			stack = append(stack, result)
+			tokens = remainingTokens
+		case ")":
+			// Return the result and the remaining tokens
+			return stack[0], tokens
+		case "+", "-", "*", "/":
+			// Handle operators
+			operators = append(operators, token)
+		default:
+			// Handle numbers
+			num, _ := strconv.Atoi(token)
+			stack = append(stack, num)
+		}
+
+		// Check if there are operators on the stack that can be applied
+		for len(operators) > 0 && len(stack) >= 2 && precedence(operators[len(operators)-1]) >= precedence(token) {
+			operator := operators[len(operators)-1]
+			operators = operators[:len(operators)-1]
+
+			num2 := stack[len(stack)-1]
+			stack = stack[:len(stack)-1]
+
+			num1 := stack[len(stack)-1]
+			stack = stack[:len(stack)-1]
+
+			// Apply the operator to the top two numbers on the stack
+			result := applyOperator(num1, num2, operator)
+			stack = append(stack, result)
+		}
+	}
+
+	// Evaluate any remaining operators on the stack
+	for len(operators) > 0 && len(stack) >= 2 {
+		operator := operators[len(operators)-1]
+		operators = operators[:len(operators)-1]
+
+		num2 := stack[len(stack)-1]
+		stack = stack[:len(stack)-1]
+
+		num1 := stack[len(stack)-1]
+		stack = stack[:len(stack)-1]
+
+		result := applyOperator(num1, num2, operator)
+		stack = append(stack, result)
+	}
+
+	// Return the final result and the remaining tokens
+	return stack[0], tokens
+}
+
+func precedence(operator string) int {
+	switch operator {
+	case "+", "-":
+		return 1
+	case "*", "/":
+		return 2
+	}
+	return 0
+}
+
+func applyOperator(num1, num2 int, operator string) int {
+	switch operator {
+	case "+":
+		return num1 + num2
+	case "-":
+		return num1 - num2
+	case "*":
+		return num1 * num2
+	case "/":
+		return num1 / num2
+	default:
+		return 0
+	}
+}
+
+func main() {
+	// Example usage
+	result := Calculator("2+(3-1)*3")
+	fmt.Println(result) // Output: 8
+
+	result = Calculator("(2-0)(6/2)")
+	fmt.Println(result) // Output: 6
+}
