fix: add bounds check to prevent out-of-range access in sparse table #2963
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Fruitchan5
requested review from
Panquesito7 and
realstealthninja
as code owners
anandfresh
approved these changes
Jul 27, 2025
mindaugl
approved these changes
Aug 14, 2025
realstealthninja
requested changes
Aug 15, 2025
| 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
| @@ -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()){ | |||
| 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
realstealthninja
requested changes
Aug 23, 2025
| @@ -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()){ |
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Description of Change
Fix the out-of-bounds access in `getMinimum()` function in `sparse_table_range_queries.cpp`.Added a boundary check to ensure stable behavior for invalid range queries.
Checklist
Notes:
This fix prevents crashes due to out-of-bounds access in RMQ function.