~josealberto4444/learning-C: Add exercise (2-7)

986e262423a1d20154b5821872182ebd883bc5fb — José Alberto Orejuela García 3 years ago e727e5c

Add exercise (2-7)

Exercise 2-7:
Write a function invert(x, p, n) that returns x with the n bits that
begin at position p inverted (i.e., 1 changed into 0 and vice versa),
leaving the others unchanged.

patch browse .tar.gz

1 files changed, 21 insertions(+), 0 deletions(-)

A 2-7/invert.c

A 2-7/invert.c => 2-7/invert.c +21 -0

@@ 0,0 1,21 @@
+#include <assert.h>
+
+/* invert: return x with the n bits that begin at position p inverted */
+unsigned
+invert(unsigned x, int p, int n)
+{
+	return x ^ (~(~0 << n) << (p - n + 1));
+}
+
+/* check some examples */
+int
+main()
+{
+	assert(9 == invert(15, 2, 2));
+	/* 15 = 1111, 9 = 1001 */
+
+	assert(1 == invert(5, 2, 1));
+	/* 5 = 101 */
+
+	return 0;
+}