String Questions at Infosys: What to Expect

String manipulation is a core skill tested in Infosys coding assessments. With 33 out of 158 total questions dedicated to strings, it represents over 20% of their problem pool. This emphasis exists because string operations mirror real-world data processing tasks common in enterprise software—parsing logs, validating inputs, transforming data formats, and handling user text. Mastering these questions demonstrates attention to detail, an understanding of edge cases, and the ability to work with fundamental data structures, which are critical for roles at Infosys.

What to Expect — Types of Problems

Infosys string problems generally fall into a few predictable categories. You will frequently encounter basic manipulation tasks like reversing a string, checking for palindromes, or converting cases. Character counting and frequency analysis is another common theme, such as finding the first non-repeating character or counting vowel/consonant occurrences. More complex problems involve string transformation—removing duplicates, replacing substrings, or compressing strings (e.g., "aaabb" becomes "a3b2"). Some questions may blend strings with simple algorithms for sorting, searching, or anagram detection. The difficulty is usually easy to moderate, focusing on clean, correct implementation rather than highly optimized, complex algorithms.

How to Prepare — Study Tips with One Code Example

Focus on mastering a few key patterns rather than memorizing solutions. Practice writing code by hand or in a simple editor to simulate test conditions. Always consider edge cases: empty strings, single characters, spaces, and special characters. For each problem, think about time and space complexity—most Infosys problems expect O(n) time solutions.

A fundamental pattern is the two-pointer technique, often used for in-place reversal or palindrome checks. Here is a clear example for reversing a string in-place (where possible) or returning a new reversed string.

def reverse_string(s: str) -> str:
    # Convert to list for in-place modification in Python's mutable sense
    chars = list(s)
    left, right = 0, len(chars) - 1
    while left < right:
        chars[left], chars[right] = chars[right], chars[left]
        left += 1
        right -= 1
    return ''.join(chars)

# Example usage
print(reverse_string("Infosys"))  # Output: "sysofnI"

Recommended Practice Order

Start with the basics. First, ensure you can traverse strings, access characters, and use built-in methods (like split(), join(), substring()). Then, practice frequency counting using arrays or hash maps. Move on to palindrome and anagram problems, which often build on counting or two-pointer approaches. Next, tackle substring and search problems, such as finding the longest substring without repeating characters or implementing a basic string search. Finally, combine these skills in transformation problems, like string compression or formatting. Consistently time yourself to build speed and accuracy.

Practice String at Infosys