Listing 1 is the example implementation (from the most recent tip) of lookup tables that can provide a default value when the item being looked up is not found.
清单1是查找表的示例实现(摘自最近的那篇技巧)，在查找失败时，它可以提供默认值。
3
Find those servers who fill the glasses and pick up empty plates from others' tables, even when they know they won't get the tip.