foo.cc: In function 'void comb(std::vector<int>&, int, int, std::vector<int>&, std::vector<std::vector<int> >&)':
foo.cc:31:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   31 |     for (int i = start; i <= nums.size() - k; i++) {
      |                         ~~^~~~~~~~~~~~~~~~~~

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