Given an unlimited supply of coins of denominations, we wish to make change for a value ; that is, we wish to find a set of coins whose total value is . This might not be possible: for instance, if the denominations are and 10 then we can make change for 15 but not for 12. Give an dynamic-programming algorithm for the following problem.Input:,; .Question: Is it possible to make change for using coins of denominations ?

Short Answer

Expert verified

The algorithm is as follows:

Create an array of size

D0=Truefori=1 to V   Di=Falseforv=1 to V   forj=1 to V

      ifxjv         Dv=DvORDvxi      else         Dv=Falsereturn DV

Step by step solution

01

Define dynamic programming 

Dynamic programming is a paradigm used for writing algorithm which helps to solve some particular type of problems more efficiently by saving the solution of subproblems and using them to get the final solution. Rather than performing the same calculation again and again, the optimal solution to subproblems are calculated and stored.

02

Determine the subproblem

ConsiderDu as sub-problem such that u=1,.,v.

Thus, according to question,Du is true if it is possible to make change for v using coins denomination.x1,x2,xn

Du=TRUE;ifitispossibletomakechangeforvFALSE;otherwise

Now, takingDu as sub-problem, if it is possible to make change forv using denomination,x1,x2,xnthen it is also possible to make change for by using same denomination with the coin.

The desired recursion is:

Here, ‘’ is the value for which we finding denomination.

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Most popular questions from this chapter

Local sequence alignment. Often two DNA sequences are significantly different, but contain regions that are very similar and are highly conserved. Design an algorithm that takes an input two strings x[1Kn]and y[1Km]and a scoring matrix δ(as defined in Exercise 6.26), and outputs substrings x'andy'of x and y respectively, that have the highest-scoring alignment over all pairs of such substrings. Your algorithm should take time O(mn).

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Give a dynamic programming algorithm that, given the locations of m cuts in a string of length , finds the minimum cost of breaking the string into m +1 pieces.

Here is yet another variation on the change-making problem (Exercise 6.17). Given an unlimited supply of coins of denominations x1,x2,x3.........xnwe wish to make change for a value v using at most k coins; that is, we wish to find a set ofkcoins whose total value is v. This might not be possible: for instance, if the denominations are 5 and 10 and k=6, then we can make change for 55 but not for 65. Give an efficient dynamic-programming algorithm for the following problem. Input: ; x1,x2,x3.........xn;k;v.Question: Is it possible to make change for v using at most k coins, of denominations x1,x2,x3.........xn?

A contiguous subsequence of a list Sis a subsequence made up of consecutive elements of S. For instance, if Sis 5,15,30,10,5,40,10

then15,30,10 is a contiguous subsequence but5,15,40 is not. Give a linear-time algorithm for the following task:Input: A list of numbers a1,a2,...,an.

Output: The contiguous subsequence of maximum sum (a subsequence of length zero has sum zero).For the preceding example, the answer would be 10,5,40,10, with a sum of 55. (Hint: For each j{1,2,...,n}, consider contiguous subsequences ending exactly at position j.)

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