What am I missing?

Question about the task

Under discussion

I adjusted my code. Now it does see it as recursion, but it is still saying the answer is wrong? Why? Even my calculator says every answer is as expected? Who can find the error? I'm currently at attempt 30 to get this thing finished.

The input is a mathematical expression in the form of a String.
The expression may include whole numbers, fractional numbers, parentheses (), spaces, negative signs -, exponents ^, sin(x), cos(x), and tan(x)
For sin(x), cos(x), and tan(x), the expression inside the parentheses should be interpreted as degrees. For example: cos (3 + 19 * 3) = 0.5
An exponent is expressed as follows: a^(1+3) would be a^4, which is equivalent to a*a*a*a.
Using recursion, evaluate the expression and calculate the number of mathematical operations. Display the result separated by spaces.
Display results that are accurate to the hundredths place, e.g. for 0.33333, display 0.33. Use the standard rules for rounding.
A negative sign before a number is also considered a mathematical operation.
Don't create additional fields in the Solution class.
Don't use indirect recursion.

Example that uses the sin, *, -, +, *, and + operations:
sin(2*(-5+1.5*4)+28)

Result:
0.5 6

Example that uses the tan and ^ operations:
tan(2025 ^ 0.5)

Result:
1 2

Requirements:

Additional fields must not be created in the Solution class.
The recurse method must display the result of evaluating the passed expression (examples are in the task conditions).
The recurse method must not be static.
The recurse method must be recursive.

package com.codegym.task.task34.task3404; import javax.script.ScriptEngine; import javax.script.ScriptEngineManager; import javax.script.ScriptException; import java.text.DecimalFormat; import java.text.NumberFormat; import java.util.ArrayList; import java.util.Arrays; import java.util.List; /* Recursion for mathematical expressions */ public class Solution { public static void main(String[] args) { Solution solution = new Solution(); solution.recurse("sin(2*(-5+1.5*4)+28)", 0); // Expected output: 0.5 6 solution.recurse("tan(2025 ^ 0.5)", 0); // Expected output: 1 2 solution.recurse("1+2.41+1", 0); // Expected 4.41 1 solution.recurse("2^2", 0); // Expected 4 1 solution.recurse(" 3 + 4 * 2 / ( 1 - 5 ) ^ 2 ^ 3", 0); //Expected 3 6 } public void recurse(final String expression, int countOperation) { //implement String currentExpression = expression; if (countOperation == 0) { countOperation = getOperationsCount(expression); } if (isNumber(currentExpression)) { NumberFormat numberFormat = new DecimalFormat("#.##"); Double result = Double.parseDouble(currentExpression); System.out.println(String.format("%s %d", numberFormat.format(result), countOperation)); return; } else if (currentExpression.contains("(")) { int lastParenthStart = currentExpression.lastIndexOf("("); int lastParenthEnd = currentExpression.indexOf(")", lastParenthStart); String mostInnerExpr = currentExpression.substring(lastParenthStart + 1, lastParenthEnd); String innerFunction = lastParenthStart > 2 ? expression.substring(lastParenthStart - 3, lastParenthStart) : "nop"; if (isNumber(mostInnerExpr)) { double mostInnerResult = Double.parseDouble(mostInnerExpr); switch (innerFunction) { case "sin": mostInnerResult = Math.sin(mostInnerResult * Math.PI / 180); lastParenthStart -= 3; break; case "cos": mostInnerResult = Math.cos(mostInnerResult * Math.PI / 180); lastParenthStart -= 3; break; case "tan": mostInnerResult = Math.tan(mostInnerResult * Math.PI / 180); lastParenthStart -= 3; break; } currentExpression = currentExpression.substring(0, lastParenthStart) .concat(String.valueOf(mostInnerResult)) .concat(currentExpression.substring(lastParenthEnd + 1)); } else { // Expression in innermost block if (innerFunction.equalsIgnoreCase("sin") || innerFunction.equalsIgnoreCase("cos") || innerFunction.equalsIgnoreCase("tan")) { currentExpression = currentExpression.substring(0, lastParenthStart + 1) .concat(String.valueOf(calcExpression(mostInnerExpr))) .concat(currentExpression.substring(lastParenthEnd)); } else { currentExpression = currentExpression.substring(0, lastParenthStart) .concat(String.valueOf(calcExpression(mostInnerExpr))) .concat(currentExpression.substring(lastParenthEnd + 1)); } } } else { currentExpression = String.valueOf(calcExpression(currentExpression)); } recurse(currentExpression, countOperation); } private double calcExpression(String expression) { String sum = expression; while (sum.contains("^") || sum.contains("*") || sum.contains("/") || sum.contains("+") || sum.contains("-") && !sum.startsWith("-")) { if (sum.contains("^")) { int index = sum.indexOf("^"); double[] aIndex = findA(sum, index); double[] bIndex = findB(sum, index); double answer = Math.pow(aIndex[0], bIndex[0]); sum = sum.substring(0, (int) aIndex[1]) + answer + sum.substring((int) bIndex[1]); } else if (sum.contains("*")) { int index = sum.indexOf("*"); double[] aIndex = findA(sum, index); double[] bIndex = findB(sum, index); double answer = aIndex[0] * bIndex[0]; sum = sum.substring(0, (int) aIndex[1]) + answer + sum.substring((int) bIndex[1]); } else if (sum.contains("/")) { int index = sum.indexOf("/"); double[] aIndex = findA(sum, index); double[] bIndex = findB(sum, index); double answer = aIndex[0] / bIndex[0]; sum = sum.substring(0, (int) aIndex[1]) + answer + sum.substring((int) bIndex[1]); } else if (sum.contains("+")) { int index = sum.indexOf("+"); double[] aIndex = findA(sum, index); double[] bIndex = findB(sum, index); double answer = aIndex[0] + bIndex[0]; sum = sum.substring(0, (int) aIndex[1]) + answer + sum.substring((int) bIndex[1]); } else if (sum.contains("-")) { int index = sum.indexOf("-"); double[] aIndex = findA(sum, index); double[] bIndex = findB(sum, index); double answer = aIndex[0] - bIndex[0]; sum = sum.substring(0, (int) aIndex[1]) + answer + sum.substring((int) bIndex[1]); } } return Double.parseDouble(sum); } private double[] findA(String sum, int index){ StringBuilder stringBuilder = new StringBuilder(); double[] a = new double[2]; for (int i = index-1; i >= 0; i--){ if (sum.charAt(i) == '^' || sum.charAt(i) == '*' || sum.charAt(i) == '/' || sum.charAt(i) == '+'){ a[1] = i+1; break; } if (sum.charAt(i) == '-' && i != 0 && sum.charAt(i-1) != '^' && sum.charAt(i-1) != '*' && sum.charAt(i-1) != '/' && sum.charAt(i-1) != '+' && sum.charAt(i-1) != '-'){ } stringBuilder.insert(0, sum.charAt(i)); if (i == 0){ a[1] = i; } } try{ a[0] = Double.parseDouble(stringBuilder.toString()); }catch (Exception e){ int x = Integer.parseInt(stringBuilder.toString()); a[0] = x * 1.0; } return a; } private double[] findB(String sum, int index){ StringBuilder stringBuilder = new StringBuilder(); double[] b = new double[2]; for (int i = index+1; i < sum.length(); i++){ if (sum.charAt(i) == '^' || sum.charAt(i) == '*' || sum.charAt(i) == '/' || sum.charAt(i) == '+' || sum.charAt(i) == '-' && i != index+1){ b[1] = i; break; } stringBuilder.append(sum.charAt(i)); if (i == sum.length()-1){ b[1] = i+1; } } try{ b[0] = Double.parseDouble(stringBuilder.toString()); }catch (Exception e){ int x = Integer.parseInt(stringBuilder.toString()); b[0] = x * 1.0; } return b; } private boolean isNumber(String expression) { if (expression == null) return false; return expression.matches("^[+-]?\\d+(\\.\\d+)?"); } public Solution() { //don't delete } private int getOperationsCount(String expression) { String[] operations = new String[] {"sin", "cos", "tan", "\\^", "\\+", "\\-", "\\*", "\\/"}; int operationsCount = 0; for (String operation : operations) { operationsCount += expression.split(operation).length - 1; } return operationsCount; } }

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Tony Roy

Level 41 , Victorville, United States

26 May 2020, 14:45

After multiple attempts, I have not been able to pass this task either. This version crashes on "2 - -1" and on "3 - 1 + 5". I tried fixing, but still no dice.

AnnemiekFF

Level 41 , Breda, Netherlands

27 May 2020, 11:23

I have also fixed the errors you pointed, and still not correct. (See new question for the code). I still have no clue what they want or wherever the problem could be. It bugs me though as this is the only question in the entire codegym that is available atm that I have not finished.

Tony Roy

Level 41 , Victorville, United States

27 May 2020, 13:31

Yes, I have not finished the course like you, but it is the first task I have not completed to this stage (and it's bugging me). After trying your "bottom up" strategy I tried a "recursive descent" model based on something from the web (#231). I would not have expected it to pass (it uses indirect recursion). But I am *really confident* that its results are right. Still the validator says results are wrong. One thought is that it is not clear how to respond in case of an invalid input string?? Also there may be a clue in having countOperation as an input to recurse. But I haven't been able to construct anything that uses that variable.