DSA — Strings

What is a String?

A sequence of characters.

# Creating strings
s = "Hello, World!"
s = str(123)

String Operations

Operation	Time Complexity
Access	O(1)
Concatenation	O(n)
Search	O(n)
Slice	O(k)

Common Operations

# Length
len(s)

# Access
first = s[0]
last = s[-1]

# Slice
substring = s[1:5]

# Find
index = s.find("World")
count = s.count("l")

# Replace
new_s = s.replace("World", "Python")

# Split
words = s.split(", ")

# Join
new_s = ", ".join(words)

# Case
s.upper()
s.lower()
s.title()

String Problems

# Check palindrome
def is_palindrome(s):
    return s == s[::-1]

# Count vowels
def count_vowels(s):
    return sum(1 for c in s.lower() if c in 'aeiou')

# Reverse string
def reverse_string(s):
    return s[::-1]

Mini Practice

1. Manipulate strings
2. Check for palindromes
3. Count character frequencies
4. Reverse a string

Up Next

Continue with Linked Lists — linked list data structure.