Question

I tried to solve project euler 31:

In England the currency is made up of pound, £, and pence, p, and
there are eight coins in general circulation:

1p, 2p, 5p, 10p, 20p, 50p, £1 (100p) and £2 (200p). It is possible to
make £2 in the following way:

1×£1 + 1×50p + 2×20p + 1×5p + 1×2p + 3×1p

How many different ways can £2 be
made using any number of coins?

with this code:

#define to2(x) ((x)/2+1)

int to5(x)
{
    int acc=1;
    for(;x>0;x-=5)
        acc+=to2(x);
    return acc;
}

int to10(x)
{
    int acc=1;
    for(;x>0;x-=10)
        acc+=to5(x);
    return acc;
}

int to20(x)
{
    int acc=1;
    for(;x>0;x-=20)
        acc+=to10(x);
    return acc;
}

int to50(x)
{
    int acc=1;
    for(;x>0;x-=50)
        acc+=to20(x);
    return acc;
}

int to100(x)
{
    int acc=1;
    for(;x>0;x-=100)
        acc+=to50(x);
    return acc;
}

int main()
{
    int test = to100(200)+1;
    printf("%d",test);
    return 0;
}

But the code gives 73685, not 73682 but I don’t know why, could someone help me plz?

Answer 1

Why do you initialize acc to 1? (It makes sense when x is a multiple of the number of the function, but only then.) change it to 0, and change the loop condition to x>=0. (If I understood your code).