Suppose we have given a coins of denominations (1, 2, 5 and 10). We have to find in how many ways can we can arrange n using these dominations. We have an array called count with 4 elements, where count[0] indicates number of coins of 1, count[1] indicates number of coins for 2 and so on.
So, if the input is like n = 27 count = [8,4,3,2], then the output will be 18 so there are 18 possible combinations some of them are
10*2 + 5*1 + 2*1 = 27
10*2 + 2*3 + 1*1 = 27
10*1 + 5*3 + 2*1 = 27
10*1 + 5*1 + 4*2 + 4*1 = 27
and so on...
To solve this, we will follow these steps −
- denom := [1,2,5,10]
- A := an array of size (n + 1) and fill with 0
- B := a new list from A
- for i in range 0 to (minimum of count[0] and n), do
- A[i] := 1
- for i in range 1 to 3, do
- for j in range 0 to count[i], do
- for k in range 0 to n + 1 - j *denom[i], do
- B[k + j * denom[i]] := B[k + j * denom[i]] + A[k]
- for k in range 0 to n + 1 - j *denom[i], do
- for j in range 0 to n, do
- A[j] := B[j]
- B[j] := 0
- for j in range 0 to count[i], do
- return A[n]
Example
Let us see the following implementation to get better understanding
denom = [1,2,5,10] def solve(n, count): A = [0 for _ in range(n+1)] B = list(A) for i in range(min(count[0], n) + 1): A[i] = 1 for i in range(1, 4): for j in range(0, count[i] + 1): for k in range(n + 1 - j *denom[i]): B[k + j * denom[i]] += A[k] for j in range(0, n + 1): A[j] = B[j] B[j] = 0 return A[n] n = 27 count = [8,4,3,2] print(solve(n, count))
Input
27, [8,4,3,2]
Output
18