mysqld_safe --skip-grant-tables &
mysql -u root
ALTER USER 'root'@'localhost' IDENTIFIED BY 'new-password';
SET PASSWORD FOR 'root'@'localhost' = PASSWORD('new-password); flush privileges; quit;
Note: this will work only if you are physically on the same server.
Online Doc: http://dev.mysql.com/doc/refman/5.7/en/resetting-permissions.html