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Dynamically allocating an array from a polynomial function string

So, I have a polynomial addition problem like the following:

(1*x+2*x^3-1*x+7)+(1+1*x^2-1*x+1*x^4)

I need to figure out how to extract numbers for coefficients and measures and inject them into a dynamically allocated 2D array (from here I can sort them and add them together before giving the answer).

I am rather lost on how to do this because polynomials can be in any order of degrees and include any number of terms. I can dynamically allocate them after retrieving all numbers. I need help:

  • Extracting all numbers
  • Differentiate between them to see if it is a ratio or an indicator
  • Let's say this happens for any number of terms.

If anyone can answer this, or at least point me in the right direction, it would be appreciated.

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2 answers


Your problem looks like its analysis and assessment.

  • Step 1: you need to parse the string assuming infix expression so that you can pull out the coefficient

  • Step2: push these coefficients into vector / deque etc. to perform polynomial calculation.

Here are some good examples:



Evaluating arithmetic expressions from a string in C ++

What is the best way to evaluate mathematical expressions in C ++?

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To extract coefficients from a string, you need to create a parser. You can use a special library like boost.spirit , you can use a special tool that creates parsers like Flex , or you can make your own by hand using regular expressions or not.

To store the coefficients, you can use std::vector<int>

using indices as cardinality of x, so for 1 * x + 2 * x ^ 3-1 * x + 7 your vector will have the data:



{ 7, -1, 0, 2 } // 7*x^0 + -1*x^1 + 0*x^2 + 2*x^3

then you don't need to sort them to add odds. To keep all polynomials, you must use std::vector<std::vector<int>>

accordingly.

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