Please, help to corrects my solution for problem on SPOJ

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C++

C++11

Hi, I was solving "Help The Commander in Chief" problem on SPOJ SPOJ.com - Problem KFSTB[^]My code is giving a wrong answer, and I'm really interested in knowing why..

My algorithm:
Use memorization to recursively calculate number of paths from the starting point to the end point.
And here's the code:

using size_type = unsigned long long int;
using ushort = unsigned short;

size_type paths(const Map &m)
{
    if (m.start() == m.end()) return 1; 
    map<ushort, size_type> h;
    h[m.end()] = 1;
    count(m, m.start(), h);
    return h[m.start()];
}

void count(const Map &m, ushort p, map<ushort, size_type> &h)
{
    for (ushort i = 1; i < m[p].size(); i++) // m[p][0] is implicity refused
    {
        if (h.find(m[p][i]) == h.end())
            count(m, m[p][i], h);
        h[p] += h[m[p][i]];
    }
}

I want to know what special cases, for example, that I didn't deal with correctly, What is fault about this algorithm (or code) ?

Thanks
- Sam

What I have tried:

I have tried some simple modifications, like trying in countHelp function to not visit the same node twice(or same p), but it didn't help, I also googled and found solutions like topological sort and dp. but actually I don't care about solving it right now..