Exercise 4-1. Write the function strindex(s,t) that returns the position of the rightmost occurrence of t in s, or -1 if there is none. The K&R strindex in Section 4.1 returns the leftmost match by scanning left-to-right and returning at the first hit. For the rightmost match there are two symmetric approaches: scan right-to-left and …
A C program to print factors of a number finds all positive integers that divide the number evenly (with no remainder). These are also called divisors. For 12: the factors are 1, 2, 3, 4, 6, and 12. Every number has at least two factors: 1 and itself. A number with exactly two factors is …
Topological sort orders the vertices of a directed acyclic graph (DAG) so that every edge points forward: if there’s an edge from u to v, then u appears before v in the ordering. It’s the algorithm behind every dependency system you’ve used — build tools compiling files in the right order, package managers resolving installs, …
Exercise 3-6. Write a version of itoa that accepts three arguments instead of two. The third argument is a minimum field width; the converted number must be padded with blanks on the left if necessary to make it wide enough. This is exactly what printf‘s %6d format does — the 6 is a minimum field …
Exercise 3-5. Write the function itob(n,s,b) that converts the integer n into a base b character representation in the string s. In particular, itob(n,s,16) should produce in s a hexadecimal string. itob generalises itoa from base 10 to any base 2–36. The only change to the digit-extraction loop is replacing n % 10 with n …
Exercise 3-4. In a two’s complement number representation, our version of itoa does not handle the largest negative number, that is, the value of n equal to −(2wordsize−1). Explain why not. Modify it to print that value correctly, regardless of the machine on which it runs. This exercise has two parts: explain the bug, then …