String Pattern Matching Naive in DSA Python - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if the pattern matches the text at position i.

DSA Python

if text[i:i+len(pattern)] == [1]:
    print(f"Pattern found at index {i}")

Drag options to blanks, or click blank then click option'

Apattern

Btext

Ctext[i]

Dpattern[i]

Attempts:

3 left

💡 Hint

Common Mistakes

Using text instead of pattern for comparison.

Comparing single characters instead of substrings.

We compare the substring of text starting at i with the pattern to check for a match.

2fill in blank

medium

Complete the code to iterate over all possible starting positions in the text.

DSA Python

for i in range(len(text) - [1] + 1):
    # check pattern match here

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Alen(pattern) - 1

Blen(text)

Clen(text) - 1

Dlen(pattern)

Attempts:

3 left

💡 Hint

Common Mistakes

Using len(text) instead of len(pattern) in the range.

Off-by-one errors in the loop range.

We iterate until the last possible start where the pattern can fit inside the text.

3fill in blank

hard

Fix the error in the code to correctly check for pattern match character by character.

DSA Python

match = True
for j in range(len(pattern)):
    if text[i+j] != [1]:
        match = False
        break

Drag options to blanks, or click blank then click option'

Apattern[j]

Bpattern[i]

Ctext[j]

Dtext[i]

Attempts:

3 left

💡 Hint

Common Mistakes

Comparing text characters with wrong indices.

Using text[i] instead of pattern[j].

We compare each character of the pattern with the corresponding character in the text.

4fill in blank

hard

Fill both blanks to complete the naive pattern matching function.

DSA Python

def naive_pattern_search(text, pattern):
    for i in range(len(text) - [1] + 1):
        match = True
        for j in range([2]):
            if text[i+j] != pattern[j]:
                match = False
                break
        if match:
            print(f"Pattern found at index {i}")

Drag options to blanks, or click blank then click option'

Alen(pattern)

Blen(text)

Attempts:

3 left

💡 Hint

Common Mistakes

Using len(text) in inner loop.

Incorrect loop ranges causing index errors.

The outer loop runs until text length minus pattern length plus one, and inner loop runs over pattern length.

5fill in blank

hard

Fill all three blanks to create a dictionary of pattern occurrences with their start indices.

DSA Python

def find_pattern_positions(text, pattern):
    positions = []
    for i in range(len(text) - [1] + 1):
        if text[i:i+[2]] == [3]:
            positions.append(i)
    return positions

Drag options to blanks, or click blank then click option'

Alen(pattern)

Blen(text)

Cpattern

Dtext

Attempts:

3 left

💡 Hint

Common Mistakes

Using len(text) instead of len(pattern) in loop or slice.

Comparing substring with text instead of pattern.

We use len(pattern) to limit the loop and substring length, and compare with the pattern.