Compilare: user.cpp: In function ‘void df(int)’: user.cpp:18: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘int search(int, int)’: user.cpp:25: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘void build()’: user.cpp:37: warning: comparison between signed and unsigned integer expressions user.cpp:53: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘void read()’: user.cpp:64: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result user.cpp:67: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result user.cpp: In function ‘void write()’: user.cpp:88: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘int search(int, int)’: user.cpp:28: warning: control reaches end of non-void function