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fix: add bounds check to prevent out-of-range access in sparse table #2963

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fix: add bounds check to prevent out-of-range access in sparse table #2963

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9 changes: 9 additions & 0 deletions range_queries/sparse_table_range_queries.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -83,10 +83,19 @@ std::vector<std::vector<T> > buildTable(const std::vector<T>& A,
template <typename T>
int getMinimum(int beg, int end, const std::vector<T>& logs,
const std::vector<std::vector<T> >& table) {
if(beg<0||end<<beg||end>=(int)table[0].size()){
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also why are we left shifting end by beg?
shouldnt it be

Suggested change
if(beg<0||end<<beg||end>=(int)table[0].size()){
if(beg < 0 || end < beg || end >= (int) table[0].size()){

cout<<"Error:querry range ["<<beg<<","<<end<<"] is invalid."<<endl;
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Suggested change
cout<<"Error:querry range ["<<beg<<","<<end<<"] is invalid."<<endl;
throw std::invalid_argument("Error:query range ["<<beg<<","<<end<<"] is invalid.");

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we can also force beg > 0 by using unsigned integer instead preferably uint32_t

return -1;
}
int p = logs[end - beg + 1];
int pLen = 1 << p;
if (p >= (int)table.size() || beg >= (int)table[p].size() || (end - pLen + 1) >= (int)table[p].size()) {
std::cerr << "Error: index out of bounds when accessing sparse table." << std::endl;
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throw an error instead

return -1;
}
return std::min(table[p][beg], table[p][end - pLen + 1]);
}

} // namespace sparse_table
} // namespace range_queries

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