#include <iostream>
#include <string>
#include <cctype>
/*
Function: isABCWord
Purpose: Check whether the letters 'a', 'b', and 'c' appear in the word
in alphabetical order (a → b → c), not necessarily consecutively.
Algorithm (efficient O(n)):
- Scan the word once.
- Track which of the letters we have already seen.
- We expect them in order: first 'a', then 'b', then 'c'.
- If we see 'b' before 'a', or 'c' before 'b', the word is NOT an ABC word.
- If we see all three in correct order, return true.
Notes:
- Case-insensitive: 'A', 'B', 'C' also count.
- Other letters are ignored.
*/
bool isABCWord(const std::string& word) {
bool seenA = false;
bool seenB = false;
for (char ch : word) {
char c = std::tolower(static_cast<unsigned char>(ch));
if (c == 'a') {
seenA = true;
}
else if (c == 'b') {
// If 'b' appears before 'a', order is broken
if (!seenA) return false;
seenB = true;
}
else if (c == 'c') {
// If 'c' appears before 'b', order is broken
if (!seenB) return false;
return true; // We found a, then b, then c in order
}
}
// If we finish scanning without seeing all three in order
return false;
}
int main() {
std::string word = "algebraic";
if (isABCWord(word)) {
std::cout << "This IS an ABC word.\n";
} else {
std::cout << "This is NOT an ABC word.\n";
}
}
/*
run:
This IS an ABC word.
*/
