Chains (sequential, router) in Prompt Engineering / GenAI - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Sequential Chains

In a sequential chain, multiple steps are executed one after another. Which statement best describes how data flows through a sequential chain?

A All steps run independently and their outputs are combined at the end.

B Each step receives input from the previous step's output and passes its output to the next step.

C The first step receives all inputs and the last step produces all outputs without intermediate processing.

D Steps randomly select inputs from the original data without following order.

💡 Hint

Think about a relay race where one runner passes the baton to the next.

In sequential chains, each step depends on the previous step's output, passing data along in order.

❓ Model Choice

intermediate

Choosing a Router Chain Use Case

You want to build a system that decides which specialized model to use based on the input type (e.g., text, image, or audio). Which chain type is best suited for this task?

A Sequential chain that processes all inputs through every model in order.

B Parallel chain that runs all models simultaneously and averages their outputs.

C Router chain that selects the appropriate model based on input characteristics.

D Single model chain that handles all input types without selection.

💡 Hint

Consider a traffic controller directing cars to different lanes based on their type.

A router chain directs inputs to the best-suited model, improving efficiency and accuracy.

❓ Predict Output

advanced

Output of a Sequential Chain Code

What is the output of the following pseudo-code for a sequential chain?

Prompt Engineering / GenAI

def step1(x):
    return x + 2

def step2(y):
    return y * 3

input_value = 4
output = step2(step1(input_value))
print(output)

A 20

B 14

C 12

D 18

💡 Hint

Calculate step1 first, then use its output in step2.

step1(4) = 6; step2(6) = 18; so output is 18.

❓ Metrics

advanced

Evaluating Router Chain Performance

You have a router chain that directs inputs to three models. After testing, you get these accuracies: Model A: 90%, Model B: 85%, Model C: 80%. The router correctly routes 95% of inputs. What is the approximate overall accuracy of the router chain?

A 88.25%

B 92.50%

C 90.00%

D 85.75%

💡 Hint

Calculate weighted accuracy considering routing correctness and model accuracies.

Overall accuracy ≈ (router accuracy * average model accuracy) + (router error * random guess accuracy). Assuming random guess accuracy is low, main factor is router accuracy times average model accuracy.

🔧 Debug

expert

Debugging a Router Chain Routing Error

Given this router chain pseudo-code, what causes the routing error?

def router(input):
    if 'image' in input:
        return 'model_image'
    elif 'text' in input:
        return 'model_text'
    else:
        return 'model_default'

input_data = 'audio file'
selected_model = router(input_data)
print(selected_model)

A The router does not handle 'audio' inputs, so it returns 'model_default' which may not exist.

B The condition 'if "image" in input' causes a syntax error due to missing colon.

C The input_data variable is not defined before calling router.

D The router function returns a list instead of a string, causing a type error.

💡 Hint

Check how the router handles inputs not matching 'image' or 'text'.

The router returns 'model_default' for inputs like 'audio file', but if 'model_default' is not implemented, this causes an error.

Practice

1. What is the main purpose of a sequential chain in GenAI?

easy

A. To run all AI steps at the same time

B. To randomly select one AI step to run

C. To run multiple AI steps one after another in order

D. To stop the AI process after the first step

Solution

1. Step 1: Understand sequential chain behavior

   A sequential chain connects AI steps so they run one after another, passing output from one to the next.

2. Step 2: Compare options to definition

   Only To run multiple AI steps one after another in order describes running steps in order, matching the sequential chain purpose.

3. Final Answer:

   To run multiple AI steps one after another in order -> Option C

4. Quick Check:

   Sequential chain = run steps in order [OK]

Hint: Sequential means steps run one after another [OK]

Common Mistakes:

• Thinking sequential means random step selection
• Confusing sequential with parallel execution
• Assuming sequential chains stop early

2. Which of the following is the correct way to define a router chain in GenAI?

easy

A. router = SequentialChain(steps=[step1, step2])

B. router = RouterChain(steps=[step1, step2], router_function=choose_step)

C. router = RouterChain(steps=step1, step2)

D. router = ChainRouter(steps=[step1, step2])

Solution

1. Step 1: Recall router chain syntax

   A router chain requires a list of steps and a router function to decide which step to run.

2. Step 2: Check each option's syntax

   router = RouterChain(steps=[step1, step2], router_function=choose_step) correctly uses RouterChain with steps list and router_function parameter. Others have wrong class names or syntax.

3. Final Answer:

   router = RouterChain(steps=[step1, step2], router_function=choose_step) -> Option B

4. Quick Check:

   RouterChain needs steps list and router_function [OK]

Hint: RouterChain needs steps list and router_function param [OK]

Common Mistakes:

• Using SequentialChain instead of RouterChain
• Passing steps without brackets as list
• Using wrong class names like ChainRouter

3. Given the code below, what will be the output?

def router_func(input_text):
    if 'weather' in input_text.lower():
        return 'weather_step'
    else:
        return 'default_step'

steps = {
    'weather_step': lambda x: 'It is sunny',
    'default_step': lambda x: 'I do not understand'
}

router_chain = RouterChain(steps=steps, router_function=router_func)

result = router_chain.run('What is the weather today?')

medium

A. 'It is sunny'

B. 'I do not understand'

C. Error: router_function missing

D. 'What is the weather today?'

Solution

1. Step 1: Analyze router function behavior

   The router_func checks if 'weather' is in the input text (case-insensitive). Input contains 'weather', so it returns 'weather_step'.

2. Step 2: Determine which step runs

   The router_chain uses 'weather_step' key to run the lambda returning 'It is sunny'.

3. Final Answer:

   'It is sunny' -> Option A

4. Quick Check:

   Input contains 'weather' -> weather_step -> 'It is sunny' [OK]

Hint: Router picks step by input keyword match [OK]

Common Mistakes:

• Ignoring case in input text check
• Confusing step keys with output strings
• Assuming default_step runs always

4. Identify the error in this router chain code snippet:

steps = {
    'step1': lambda x: 'Hello',
    'step2': lambda x: 'Bye'
}

def router_func(input_text):
    if 'hello' in input_text:
        return 'step1'
    else:
        return 'step3'

router_chain = RouterChain(steps=steps, router_function=router_func)
result = router_chain.run('hello there')

medium

A. Lambda functions require two arguments

B. steps dictionary keys are not strings

C. router_function is missing in RouterChain

D. router_func returns a step key not in steps dictionary

Solution

1. Step 1: Check router_func return values

   router_func returns 'step1' if 'hello' in input, else 'step3'. Input contains 'hello', so returns 'step1'.

2. Step 2: Verify steps dictionary keys

   Steps dictionary has keys 'step1' and 'step2', but no 'step3'. Returning 'step3' would cause error if input changed.

3. Final Answer:

   router_func returns a step key not in steps dictionary -> Option D

4. Quick Check:

   Router returns unknown step key 'step3' [OK]

Hint: Router must return keys present in steps dict [OK]

Common Mistakes:

• Ignoring missing step keys in router return
• Assuming lambda needs multiple args
• Forgetting to pass router_function parameter

5. You want to build a GenAI system that first summarizes a text, then translates it to French, but only if the text is longer than 100 words. Which chain setup is best?

hard

A. Use a sequential chain with a router function that skips translation if text is short

B. Use a router chain that chooses between summarization or translation only

C. Use two separate sequential chains running independently

D. Use a sequential chain that always runs summarization then translation

Solution

1. Step 1: Understand task requirements

   The system must summarize first, then translate only if text is longer than 100 words.

2. Step 2: Choose chain type matching conditional flow

   A sequential chain with a router function can run summarization step first, then decide to run translation step based on text length.

3. Step 3: Evaluate other options

   Router chain alone can't enforce sequential order; two separate chains won't coordinate; always running translation ignores condition.

4. Final Answer:

   Use a sequential chain with a router function that skips translation if text is short -> Option A

5. Quick Check:

   Sequential + router for conditional step flow [OK]

Hint: Combine sequential steps with router for conditional logic [OK]

Common Mistakes:

• Using router chain alone without sequence
• Running translation always ignoring condition
• Splitting steps into independent chains