gondola.cpp: In function 'int valid(int, int*)':
gondola.cpp:7:65: warning: comparison of integer expressions of different signedness: 'std::set<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
7 | set<int> s; for(int i=0; i<n; i++) s.insert(S[i]); if (s.size()<n) return 0;
| ~~~~~~~~^~
/usr/bin/ld: /tmp/ccSJrKuh.o: in function `main':
grader.cpp:(.text.startup+0xb6): undefined reference to `valid'
/usr/bin/ld: grader.cpp:(.text.startup+0x108): undefined reference to `countReplacement'
/usr/bin/ld: grader.cpp:(.text.startup+0x132): undefined reference to `replacement'
collect2: error: ld returned 1 exit status