find /home/user/subdir/ -ctime -30 \( -path/home/user/subdir/tmp \) -prune -o -print > /root/new_files.txt
find /home/user/subdir/ -path /home/user/subdir/tmp/ -prune -o -ctime -30 -type f > /root/new_files.txt
find /home/user/subdir/ -ctime -30 -and -not \( -path /home/user/subdir/tmp -prune \) -print > /root/new_files.txt