Two matrices are equal if and only if they have the same dimensions (same number of rows and same number of columns) and every corresponding pair of elements is equal: A[i][j] == B[i][j] for all i, j. If the dimensions differ, equality is impossible. This program checks both conditions. The original had void main(), exit(1) …
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 …
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 C program shows how to mask password input with asterisks (*) — exactly what you see on a login screen, where each character you type is hidden behind a *. The trick is to read the keyboard without echoing the typed character to the screen, print a * in its place, and store the …