/in/foo.cc: In function 'int main()':
/in/foo.cc:15:37: error: 'memset' was not declared in this scope
  memset(&ivec[0], 0, n * sizeof(int));
                                     ^
/in/foo.cc:16:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (i = 0; i < ivec.size(); i += 2)
              ~~^~~~~~~~~~~~~
/in/foo.cc:22:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (j = (i % 2 ? 0 : 1); j < ivec.size(); j += 2)
                             ~~^~~~~~~~~~~~~
/in/foo.cc:26:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    else if (j == ivec.size() - 1) { left = ivec.size() - 2; right = 0; }
             ~~^~~~~~~~~~~~~~~~~~
/in/foo.cc:33:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (j = (i % 2 ? 1 : 0); j < ivec.size(); j += 2)
                             ~~^~~~~~~~~~~~~
/in/foo.cc:38:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (i = 0; i < ivec.size(); ++i)
              ~~^~~~~~~~~~~~~
/in/foo.cc:13:12: warning: unused variable 'k' [-Wunused-variable]
  int i, j, k;
            ^