# Program for Derivative of a Polynomial

Given a polynomial as string and a value. Evaluate polynomial’s derivative for the given value.

Note: The input format is such that there is a whitespace between a term and the ‘+’ symbol

The derivative of p(x) = ax^n is p'(x) = a*n*x^(n-1)

Also, if p(x) = p1(x) + p2(x)

Here p1 and p2 are polynomials too

p'(x) = p1′(x) + p2′(x)

Input : 3x^3 + 4x^2 + 6x^1 + 89x^0 2 Output :58 Explanation : Derivative of given polynomial is : 9x^2 + 8x^1 + 6 Now put x = 2 9*4 + 8*2 + 6 = 36 + 16 + 6 = 58 Input : 1x^3 3 Output : 27

We split the input string into tokens and for each term calculate the derivative separately for each term and add them to get the result.

`// CPP program to find value of derivative of ` `// a polynomial. ` `#include <bits/stdc++.h> ` `using` `namespace` `std; ` ` ` `long` `long` `derivativeTerm(string pTerm, ` `long` `long` `val) ` `{ ` ` ` `// Get coefficient ` ` ` `string coeffStr = ` `""` `; ` ` ` `int` `i; ` ` ` `for` `(i = 0; pTerm[i] != ` `'x'` `; i++) ` ` ` `coeffStr.push_back(pTerm[i]); ` ` ` `long` `long` `coeff = ` `atol` `(coeffStr.c_str()); ` ` ` ` ` `// Get Power (Skip 2 characters for x and ^) ` ` ` `string powStr = ` `""` `; ` ` ` `for` `(i = i + 2; i != pTerm.size(); i++) ` ` ` `powStr.push_back(pTerm[i]); ` ` ` `long` `long` `power = ` `atol` `(powStr.c_str()); ` ` ` ` ` `// For ax^n, we return a(n-1)x^(n-1) ` ` ` `return` `coeff * power * ` `pow` `(val, power - 1); ` `} ` ` ` `long` `long` `derivativeVal(string& poly, ` `int` `val) ` `{ ` ` ` `long` `long` `ans = 0; ` ` ` ` ` `// We use istringstream to get input in tokens ` ` ` `istringstream is(poly); ` ` ` ` ` `string pTerm; ` ` ` `while` `(is >> pTerm) { ` ` ` ` ` `// If the token is equal to '+' then ` ` ` `// continue with the string ` ` ` `if` `(pTerm == ` `"+"` `) ` ` ` `continue` `; ` ` ` ` ` `// Otherwise find the derivative of that ` ` ` `// particular term ` ` ` `else` ` ` `ans = (ans + derivativeTerm(pTerm, val)); ` ` ` `} ` ` ` `return` `ans; ` `} ` ` ` `// Driver code ` `int` `main() ` `{ ` ` ` `string str = ` `"4x^3 + 3x^1 + 2x^2"` `; ` ` ` `int` `val = 2; ` ` ` `cout << derivativeVal(str, val); ` ` ` `return` `0; ` `} ` |

*chevron_right*

*filter_none*

Output:

59

This article is contributed by **Ankit Jain** . If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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