/in/foo.cc: In function 'int main()':
/in/foo.cc:37:18: warning: 'root' may be used uninitialized in this function [-Wmaybe-uninitialized]
     son* p=pp[x].s;
                  ^
/in/foo.cc:91:13: note: 'root' was declared here
     int i,j,root;
             ^~~~