Slides: Using Stacks and Queues

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# Using Stacks and Queues
## CSC 161 – April  9, 2026

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# Agenda for Today
1. Quiz
2. Department Events
3. Upcoming Work
4. Discussion
5. Lab
6. Wrap Up

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# Quiz

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# Department Events

## CS Poster Sessions: Wednesday and Thursday this week
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   Wednesday, April 8th and Thursday, April 9th from 4:15–5:45pm in HSSC A1231  
   Snacks (including fresh fruit) will be provided!
]

## Ali Akgun '93 Visit
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   Watch for announcements about events with Ali Akgun (CS alum and Microsoft VP) happening next week.
]

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# Upcoming Work

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# Homework: Lightcycle
**Due:** Thursday, April 9th

## Questions?

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# Discussion

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# Search Algorithm 1
.left-col-40[
```nohighlight
stack_search(start, goal):
   s is an empty stack
   set_visited(start)
   push(s, start)

while !empty(s):
      p = pop(s)
      if p == goal:
         Success!

for dir in [↑, →, ↓, ←]:
         if valid_move(p, dir):
            n = move(p, dir)
            if !is_visited(n):
               set_visited(n)
               push(s, n)
```
]
--
.right-col-60[
<img src="../files/mouse.png" alt="A four by four grid showing a mouse at the starting position and cheese at the destination." width="75%">
]

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# Search Algorithm 2
.left-col-40[
```nohighlight
queue_search(start, goal):
   q is an empty queue
   set_visited(start)
   add(q, start)

while !empty(q):
      p = take(q)
      if p == goal:
         Success!

for dir in [↑, →, ↓, ←]:
         if valid_move(p, dir):
            n = move(p, dir)
            if !is_visited(n):
               set_visited(n)
               add(q, n)
```
]
.right-col-60[
<img src="../files/mouse.png" alt="A four by four grid showing a mouse at the starting position and cheese at the destination." width="75%">
]

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# Discussion: Search Algorithms
**Items for think, pair, share:**

1. Can you think of a concise way to describe the behavior of the stack-based search algorithm?

2. Can you think of a concise way to describe the behavior of the queue-based search algorithm?

3. Think of a problem that one of these search algorithms could help you solve.
   Does it matter which algorithm you use?

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# Homework: Pathfinding
**Due:** Thursday, April 23rd

Let's look at the assignment and some demo programs.

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# Lab Time

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# Wrap Up

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# Peer Educator Evaluations

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Fill out the form at <https://tinyurl.com/26S-mentor-evals> to evaluate mentors and other peer educators you've worked with this semester.

## Token Opportunity
If every student in the class completes the mentor evaluation before Monday I will give you all one additional token.
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<img src="../files/26S-mentor-evals-qr.png" width=80%>
]

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# Wrap Up

## Week 10 Lab Report
Submit your completed `string_stack.c`, `string_stack.h`, `string_queue.c`, and `string_queue.h` files.

## Lightcycle Assignment
The assignment is due at 10pm tonight, or on Saturday if you use a token.

## Office Hours
I'm happy to meet to discuss how things are going in the class, or to help with specific concepts if you are having trouble.
Book a time at <https://calendly.com/curtsinger/office-hours>.

## Reading
I am working on a reading for Tuesday's class.
I hope to have it posted on Friday.