Computing x raised to the power n (written xn) naively requires n multiplications. Binary exponentiation (also called fast power or exponentiation by squaring) reduces this to O(log n) multiplications by halving the exponent at each step: if n is even, compute xn/2 and square it; if n is odd, multiply x by xn-1. The original …
The standard library’s strlen() counts characters in a string by walking from the first character until it reaches the null terminator (‘\0’) — the zero byte that marks the end of every C string. Implementing strlen() yourself is a classic exercise that teaches exactly how strings work in C. The original post had two serious …
This program converts a given number of days into years, weeks, and remaining days using integer division and modulo arithmetic. The formula uses 365 days per year and 7 days per week (leap years are ignored). It is a straightforward exercise in chained division and remainder operations. The original post used void main() and broken …
A cube is a three-dimensional shape with six equal square faces. Given the side length s, the surface area is 6s² (six faces, each with area s²) and the volume is s³. This program reads the side length and computes both values using only basic arithmetic — no need for pow() and the -lm flag …
Checking whether one string contains another is one of the most common string operations in C. The standard library provides strstr() in <string.h> — it returns a pointer to the first occurrence of the substring in the main string, or NULL if not found. The position of the match is calculated by subtracting the start …
This program reads N integers into a dynamically allocated array and computes their sum using pointer arithmetic instead of array subscript notation. Understanding the equivalence between *(a + i) and a[i] is fundamental to C — both produce identical machine code. The program also demonstrates malloc() and free() for runtime-sized arrays. The original post used …