Compilare: user.cpp: In function ‘int Union(int, int)’: user.cpp:40:1: warning: no return statement in function returning non-void [-Wreturn-type] } ^ user.cpp: In function ‘int main()’: user.cpp:68:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0;j<gr[i].size();j++) ^ user.cpp:82:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0;j<gr[min].size();j++) ^ user.cpp: In function ‘char nextch()’: user.cpp:13:36: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread(buf, BUF_SIZE, 1, fi); ^