Exercises · T07 strings

Covers: std::string operations, indexing, find/substr, <cctype>, getline, word algorithms (two-pointer, boundary events), C-strings. Lectures L21–L22 (and L04's getline rules). Outcomes PF-11.x.

12 exercises · ladder 🟢 → 🔴.

PF-E-079 · Name Greeting

Difficulty: Beginner · Lecture: L21 · Outcomes: PF-11.1 Prerequisites: E-001 Problem: Read a full name (may contain spaces) with getline and print Hello, <name>! plus the name's length. Input: one line · Output: greeting + length. Sample: Ada Lovelace → Hello, Ada Lovelace! / length: 12 Hints: getline, not cin >> — spaces matter.

PF-E-080 · Initials Extractor

Difficulty: Beginner · Lecture: L21 · Outcomes: PF-11.1, PF-11.2 Prerequisites: E-079 Problem: Read a full name; print the uppercase initials (first letter of each word) followed by periods. Input: one line · Output: initials. Sample: ada lovelace → A.L. Hints: first character is an initial; every letter after a space is too.

PF-E-081 · Vowel/Consonant Census

Difficulty: Beginner · Lecture: L21 · Outcomes: PF-11.2 Prerequisites: E-080 Problem: Read one word; count vowels, consonants, and non-letters (using <cctype>), case-insensitively. Print all three. Input: one word · Output: three counts. Sample: R2-D2 → vowels: 0 / consonants: 2 / other: 3 Hints: tolower first; a letter that isn't a vowel is a consonant.

PF-E-082 · Word Count (robust)

Difficulty: Foundational · Lecture: L22 · Outcomes: PF-11.2, PF-11.4 Prerequisites: E-081 Problem: Read a whole line; count words correctly despite double spaces, leading/trailing spaces, and tabs. Print the count and the longest word's length. Input: one line · Output: count + longest length. Sample: one two three → words: 3 / longest: 5 Hints: the boundary-event state machine (L22); track current word length as you scan.

PF-E-083 · String Reversal (both ways)

Difficulty: Foundational · Lecture: L22 · Outcomes: PF-11.3 Prerequisites: E-082 Problem: Read a line. Print it reversed two ways: (1) a new reversed string built with +=, (2) in-place two-pointer reversal of a copy. Print both and confirm equal. Input: one line · Output: two reversed lines + verdict. Sample: abc de → ed cba / ed cba / match: yes Hints: method 2 needs std::string& — reference parameters preview.

PF-E-084 · Palindrome Judge (case/space insensitive)

Difficulty: Foundational · Lecture: L22 · Outcomes: PF-11.3, PF-11.4 Prerequisites: E-083 Problem: Read a line; judge palindrome ignoring case, spaces, and punctuation (digits count as characters). Print verdict and the cleaned string used. Input: one line · Output: verdict + cleaned string. Sample: A man, a plan! → not palindrome / cleaned: amanaplan Hints: clean into a new string first, then two-pointer judge — two passes beat one clever one.

PF-E-085 · Substring Finder with All Positions

Difficulty: Foundational · Lecture: L21 · Outcomes: PF-11.2 Prerequisites: E-084 Problem: Read a text line and a search word. Print every position (0-based) where the word occurs and the total count. Overlaps count (e.g. aa in aaaa occurs at 0, 1, 2). Input: two lines · Output: positions + count (or none). Sample: text ababab, word ab → positions: 0 2 4 / count: 3 Hints: find with a start position in a loop; advance by one for overlaps.

PF-E-086 · Case Normalizer

Difficulty: Intermediate · Lecture: L22 · Outcomes: PF-11.2, PF-11.3 Prerequisites: E-085 Problem: Read a line; produce the "title case" version: first letter of each word uppercase, all other letters lowercase. Preserve all non-letter characters and spacing exactly. Input: one line · Output: normalized line. Sample: hello, C++ WORLD! → Hello, C++ World! Hints: boundary events tell you when a word starts; tolower/toupper per char.

PF-E-087 · CSV Tokenizer

Difficulty: Intermediate · Lecture: L22 · Outcomes: PF-11.2, PF-11.4 Prerequisites: E-086 Problem: Read a comma-separated line (e.g. 12,7,,9); split into tokens and print each on its own numbered line. Empty fields (between consecutive commas) must appear as empty tokens. Print the token count. Input: one CSV line · Output: numbered tokens + count. Sample: 12,7,,9 → 1: 12 / 2: 7 / 3: (empty) / 4: 9 / count: 4 Hints: don't forget the final token after the last comma (L22's classic bug).

PF-E-088 · C-String Walk (char buffer)

Difficulty: Intermediate · Lecture: L17 · Outcomes: PF-11.3 Prerequisites: E-087 Problem: Copy a read word into a char buffer[32] (validate length ≤ 30 first). Walk the buffer with the terminator scan (while (buf[i] != '\0')) to count letters vs digits, then print the buffer in reverse using the same walk backwards. No std::string in the processing code. Input: one word · Output: letter/digit counts + reversed buffer. Sample: ab12 → letters: 2 / digits: 2 / reversed: 21ba Hints: find the length first by walking forward, then walk backward from length−1.

PF-E-089 · Caesar Cipher (encrypt + decrypt)

Difficulty: Advanced Introductory · Lecture: L22 · Outcomes: PF-11.2, PF-11.4 Prerequisites: E-088 Problem: Read a shift k (1–25) and a line. Encrypt: letters shift by k (wrapping A–Z / a–z), all other characters unchanged. Print the ciphertext. Then decrypt it back and print, confirming it matches the input. Input: integer + line · Output: ciphertext + decrypted plaintext. Sample: k=3, Hello, World! → Khoor, Zruog! / then Hello, World! Hints: per char: if upper, 'A' + (ch - 'A' + k) % 26 — the modular wrap; decrypt is shift 26−k.

PF-E-090 · Word Frequency Table

Difficulty: Advanced Introductory · Lecture: L22 · Outcomes: PF-11.4, PF-9.3 Prerequisites: E-089 Problem: Read a line of lowercase words (space-separated, ≤ 20 words, each ≤ 15 chars). Build a frequency table without std::map: parallel arrays of distinct words and counts. Print each distinct word with its count, in first-appearance order, then the most frequent word (first wins ties). Input: one line · Output: table + winner. Sample: a b a c b a → a: 3 / b: 2 / c: 1 / top: a Hints: for each word, linear-search the distinct list — found: increment; missing: append.