• A queue is another special type of list, where the elements are
  • Inserted only at the rear of the list
  • Deleted only at the front of the list
• Queue is often called FIFO (First-In First-Out) structure
  • ไม่เหมือนกับ 07 Stack and its Applications นะ เพราะอันนี้คือ LIFO

Queue Operations

• enqueue: Insert an element at the rear of the queue
  • Returns true if the operation was successful.
• dequeue: Remove the element at the front of the queue and return it.
• queueFront get the value at the front of the queue
• queueRear get the value at the rear of the queue

Application of Queues

• Prefix expression evaluation
• Round Robin scheduling

Prefix Expression

• Expression that the operator comes before two operands
  Ex. + 5 6
  – * 4 3 + 1 1
• Prefix Expression is parenthesis-free
• เลื่อนอันข้างไปหลัง Queue เรื่อย ๆ จนกว่า 3 อันข้างหน้าจะได้เป็น (1) Operator (2,3) Operand
  • สุดท้ายจะได้เลขออกมา 1 ตัว

Round Robin Scheduler

• A round-robin scheduler is used to fairly allocate a limited resource that must be shared with a larger demand of users.
• It gives each process a unit of time, then moves to the next process, continues until all processes completed