Compilare: main.cpp: In function 'void outputCombinations()': main.cpp:20:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(stack.size() < k) { ~~~~~~~~~~~~~^~~ main.cpp:33:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if( stack.back() < n - (k - stack.size()) ) { ~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~ main.cpp:37:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(stack.size() < k) { ~~~~~~~~~~~~~^~~ main.cpp:16:32: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen(FOUT, "w", stdout); ^ main.cpp: In function 'void read()': main.cpp:61:30: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen(FIN, "r", stdin); ^