As an army commander, you have to plan all the tasks for the soldiers, so that they can execute them. This process is called command.
You need to store the leaves hierarchically, sometimes you will count the leaves. Tree will be a suitable structure to facilitate leaf counting.
Apply singleton to maintain a single phone line between the two sides indefinitely instead of repeatedly establishing and disconnecting multiple phone lines for efficiency.
Having been with you for a long time, your robot has memories that regular manufacturing can't produce, now you want to clone it. Prototype will be your remedy.
As the coach of a strong team, you plan to attack to find a goal and then prioritize possession to preserve the score. This combination is called strategy.