Compilare: main.cpp: In function 'void bfsback(int)': main.cpp:37:34: warning: suggest parentheses around assignment used as truth value [-Wparentheses] if(dist[next]=dist[first]-1){ ^ main.cpp: In function 'int main()': main.cpp:70:32: warning: format '%d' expects argument of type 'int', but argument 3 has type 'std::set<int>::size_type {aka long unsigned int}' [-Wformat=] fprintf(fout,"%d\n",st.size()); ^ main.cpp:57:37: warning: ignoring return value of 'int fscanf(FILE*, const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] fscanf(fin,"%d%d%d%d",&n,&m,&x,&y); ^ main.cpp:59:29: warning: ignoring return value of 'int fscanf(FILE*, const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] fscanf(fin,"%d%d",&a,&b); ^