Character Frequency
A frequency table maps each possible character to a counter.
What is Character Frequency?
A frequency table maps each possible character to a counter.
Count occurrences of each lowercase letter.
Important points
- Compile with warnings enabled and fix every warning.
- Know the lifetime and type of every value.
- Validate input and keep array bounds explicit.
C and C++ code examples
main.c
#include <stdio.h>
int main(void) {
const char *text = "banana"; int counts[26] = {0};
// Convert each lowercase letter to an array index.
for (; *text; ++text) ++counts[*text - 'a'];
for (int i = 0; i < 26; ++i) if (counts[i]) printf("%c=%d\n", 'a' + i, counts[i]);
}
a=3
b=1
n=2C++
main.cpp
#include <array>
#include <iostream>
#include <string>
int main() {
std::string text = "banana"; std::array<int, 26> counts{};
// Convert each lowercase letter to an array index.
for (char character : text) ++counts[character - 'a'];
for (size_t i = 0; i < counts.size(); ++i) if (counts[i]) std::cout << char('a' + i) << '=' << counts[i] << '\n';
}
a=3
b=1
n=2C and C++ comparison
Use the character offset from a as the array index and print only nonzero counts.
C
C exposes small procedural APIs and makes representation details explicit.
C++
C++ retains the low-level model while adding safer library types and abstractions.
Practice exercises
Run both versions, then modify them to observe the different language guarantees.
- Add invalid and boundary-value inputs.
- Compile with -Wall -Wextra -Wpedantic.
- Move reusable declarations into a header and implementation file.