Search and find operations in Intro to Computing - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Linear Search

Imagine you have a list of names on a paper. You want to find if the name "Alice" is in the list by checking each name one by one from the start.

Which description best matches this search method?

A Check each item from start to end until you find "Alice" or reach the end.

B Jump to the middle of the list and decide which half to search next.

C Sort the list first, then look for "Alice" using a fast method.

D Randomly pick names until you find "Alice".

💡 Hint

Think about checking names one by one in order.

Linear search means checking each item in order until the target is found or the list ends.

❓ trace

intermediate

Trace Binary Search Steps

You have a sorted list: [2, 4, 6, 8, 10, 12, 14]. You want to find the number 10 using binary search.

Which sequence of middle elements will the search check?

A 8, 10

B 8, 12, 10

C 10

D 6, 10

💡 Hint

Binary search picks the middle element each time and narrows down the search.

First middle is 8, since 10 > 8, search right half. Next middle is 12, since 10 < 12, search left half. Next middle is 10, found target.

❓ identification

advanced

Identify the Error in Search Algorithm

Consider this pseudocode for searching a value in a list:

start = 0
end = length(list) - 1
while start <= end:
  mid = (start + end) // 2
  if list[mid] == target:
    return mid
  elif list[mid] < target:
    start = mid + 1
  else:
    end = mid - 1
return -1

What is the mistake in this binary search implementation?

A The update of 'end' and 'start' is reversed; 'start' should increase when list[mid] < target.

B The function should return mid + 1 when the target is found.

C The condition in the while loop should be start < end, not start <= end.

D The calculation of 'mid' should use floating division instead of integer division.

💡 Hint

Think about which half to search next when the middle value is less than the target.

If list[mid] is less than target, the search should continue in the right half, so 'start' must be updated to mid + 1, not 'end'.

❓ Comparison

advanced

Compare Search Methods Efficiency

Which statement correctly compares linear search and binary search on a sorted list of 1,000,000 items?

A Linear search is faster because it checks items one by one, which is simpler.

B Linear search is faster because binary search requires sorting first.

C Both searches take the same time because they look for the same item.

D Binary search is faster because it divides the list and eliminates half each time.

💡 Hint

Think about how many items each method checks in the worst case.

Binary search reduces the search space by half each step, making it much faster on large sorted lists.

🚀 Application

expert

Find the Number of Comparisons in Binary Search

You use binary search to find a number in a sorted list of 1023 elements.

What is the maximum number of comparisons binary search will make before concluding?

A 11

B 9

C 10

D 8

💡 Hint

Binary search maximum comparisons relate to the power of 2 just greater than the list size.

Binary search maximum comparisons = ceiling of log2(n). For 1023, log2(1023) ≈ 9.99, so max comparisons = 10.