Errata List for "Programming Challenges: The Programming
Contest Training Manual" by Steven Skiena and Miguel Revilla
Particularly serious errata are denoted with a (*)
Send errata to skiena@cs.sunysb.edu
Last addition: February 22, 2012
=================================================================
Page 12 -- The example using -MAXINT as sentinel is misleading
because the C language family uses 2's complement arithmetic, and
-MAXINT may not be the very smallest integer. For such arithmetic,
MININT = -MAXINT - 1 Of course, the value of the sentinel must be
less than that of every legal input, which will not be true if the
input contains MININT.
(*) Page 12 -- In the while body, the statement a[i] = a[i-1]; should be
a[i+1] = a[i] ;
Page 12, line -1 -- "the notation p.y and p.y" should be
"the notation p.x and p.y"
Page 19, row -2 of table -- "Write the file name in MSDOS 8.3 format"
should be "Write the file name exactly as it's at the
input file".
Page 26, paragraph Notes 1.2, line 1 -- "n x n" should be "m x n"
Page 30, line -13 -- "insertion on deletion" should be
"insertion or deletion"
Page 36, function rank_card: printf statement should use %c as
format indicators, not %d.
(*) Page 42, Input section line 1 -- 'n < 3000' should be 'n <= 3000'
Page 53, line -2 -- "more than" should be "more than one"
Page 55, line 11 -- "jolly number" should be "jolly jumper"
Page 83, line 10 -- We incorrectly claim our selection sort
implementation, as written, is stable. In fact, selection sort can be
*made* stable while running in the same $O(n^2)$ worst case time by
(a) ensuring that min is set to the first instance of the smallest element,
as it appears to be now, and
(b) bubbling this element up into the proper position instead of swapping
it. This might require moving up to $n$ other elements in the process,
but since we just compared all these elements to find the min, it at
most doubles the number of operations.
(*) Page 106, function subtract_bignum -- Initialize the result of bignum *c
by adding a missing call at the top to initialize_bignum(c);
Page 110, line 22 -- The binary value of 371 base 8 is 11111001 base 2,
not 10111001.
(*) Page 114, line -2 -- "A simpler method results" should be
"We can compute the fraction associated with a repeating decimal"
Page 115, line 15 -- $c[i]x^n$ should be $c[i]x^i$
Page 120, clarification -- Make sure you handle the case of single-digit
palindromes!
(*) Page 133, line -3 -- "0 and 1" should be "-1 to 1"
(*) Page 134, line -14 -- "exactly k ascending sequences or runs" should
be "exactly k descents (p(j) > p(j+1)) or k+1 runs"
(*) Page 134, line -10 -- The Eulerian number formula should be
R(n,k) = (k+1)R(n-1,k) + (n-k)R(n-1, k-1)
(*) Page 135, line 7 -- the set partition formula should be
k * ((n-1) partition k) + ((n-1) partition (k-1))
where (n partition k) is the number of ways to partition n unique items
(*) page 135, line 17 -- the basis conditions of the integer partition
formula are wrong. They should be:
f(n, k) = f(n, n) when k > n
f(n, 1) = 1
f(0, 0) = 1
f(1, 1) = 1
Page 147, line -5 -- The tenth prime number is 29, not 27.
Page 152, line 13 -- delete "it will"
(*) Page 155, line 25 -- m[1]b[1] = 1 (mod m[2]) should be
m[1]b[2] = 1 (mod m[2])
Page 159, output section, line 3: Change the last line to
"which minimizes |X|+|Y|. If the ambiguity persists, you should output
that pair for which X<=Y."
Page 163, line 17 -- "required" should be "required)"
(*) Page 171, line 5 -- There have been reports that this program crashes
because a[i] is not initialized. I have not been able to reproduce this,
put perhaps my compiler is explicitly initializing certain things to zero.
There have been other reports that the i=0..k-1 loop should be i = 1..k-1,
because k =1 when this function is called the first time, so the first
element of the permutation is stored in a[1]. My sense is that this
is true.
Page 179, line 9 -- "and and" should be "and"
Page 184, figure caption -- "on step" should be "one step"
Page 206, lines 6-7 -- "each each" should be "each"
Page 213, line 13 -- "he has must stay" should be "he must stay"
Page 217, line 8 -- We begin with "an" (not "a") overview..
Page 221, Prim's implementation -- Should declare
int parent[MAXV]; /* records tree topology */
(it was used as a global variable in our implementation)
Page 222, line 13 -- The loop should run from starting i=1, not i=2
as in the text. It doesn't really matter for Prim's algorithm, but this
preserves similarity with Dijkstra's algorithm (see errata below)
Page 224, Dijkstra's implementation -- Should declare
int parent[MAXV]; /* records tree topology */
(it was used as a global variable in our implementation)
(*) Page 224, line -12 -- The loop should run from starting i=1, not i=2
as in the text. This causes problems on shortest paths not starting from
vertex 1.
(*) Page 224 -- Another MAXINT related issue arises in Dijkstra's algorithm.
The elements of the 'distance' vector are all initialized with MAXINT as
an "infinity" value. However, when you make a test such as
if(distance[w] > (distance[v]+weight))
and distance[v] is MAXINT, then the sum will overflow and probably be
negative, misleading the program. The solution is to define a smaller
infinity constant, such as:
#define INF MAXINT/2
or even smaller -- as indeed you will find if you carefully at the .h files
of our code. It was not mentioned in the text, however.
(*) Page 226 -- The same MAXINT issue applies to Floyd's algorithm as well.
Page 227, 5th text paragraph, line 1 -- "using using" should be "using"
(*) Page 243 -- Sample Input section, line -10
3 1 2 3 2 2 3
must be broken in two lines
3 1 2 3
2 2 3
Page 255, line 4 -- should explicitly declare "int floors_walked"
for clarity (it is implicitly so declared in C)
Page 257, line 5 of Outpur section (the only formula) --
The last character is a 'i' that must be eliminated.
Page 268, first paragraph (after quote), line 2 --
"grid distance measure grid" should be "grid distance measure"
(*) page 270, function diagonal_order -- row/column indices are reversed
or inconsistent with previous functions for parameters of process(int,int).
Page 272, under Geometrical Coordinates, the formula should be --
(xg, yg) = (d (yt + (xt cos(60 degrees))), d xt sin(60 degrees))
page 274, top right circle in the picture -- second line of the center
label should be written in italics/math style. The bottom right circle
should be printed as "(0,3)" rather than "(0.3)".
(*) Page 276 Paragraph starts with "Determining how many plates...", line 3 --
"namely, (r,c-1) and (r,c)" should be "namely, (r+1,c-1) and (r+1,c)"
(*) Page 277 function plates_on_top, first call to hex_to_array --
hex_to_array(row,yh-row,&xla,&yla);
should be hex_to_array(row,yh-(row-xh),&xla,&yla);
because (row-xh) is the number of rows above the plate on row xh,
and for each row above we have to go left by 1
according to the particular coordinate system.
(*) Page 278, last line -- The formula is wrong. A correct formula is:
d(f,s) = R*acos( (sin(l[f])*sin(l[s])) + (cos(l[f])*cos(l[s])*cos(dg)) )
where R is the radius of the Great circle, dg = longitude(f)-longitude(s),
and l[f] = lattitude of f.
Page 292 line 3 -- "(0,b) where it crosses the x-axis." should be
"(0,b) where it crosses the y-axis."
(*) Page 293, line -2 -- note that the tangent goes to infinity for
perpendicular lines and zero for parallel lines
Page 295, line -4 -- cos(theta) = sin(theta + pi/2) should be
cos(theta) = sin(-theta + pi/2)
Page 300, line -1 --
The second reference to "d" must be removed as redundant.
(*) Page 303, lines 2, 4, 6 -- The descriptions of the arc functions
should read "Return the arc * of a, an angle in [.."
(*) Page 314, function segments_intersect -- under if(same_lineQ(l1,l2)):
The 3rd and 4th calls to point_in_box share identical parameters.
The 4th call was supposed to be point_in_box(s2.p2,s1.p1,s1.p2) );
In fact, neither of the 3rd or 4th calls are really necessary.
(*) Page 315, paragraph 4 -- We misuse the term "acute" angle here
and elsewhere in this section. A reflex angle is one which is > 180 degrees,
hence the proper term is "non-reflex".
(*) Page 315 Last text paragraph, line 2 --
"Negative area results if point c is to the left of a->b" should be
"Positive area results if point c is to the left of a->b"
(*) Page 316, line 4 -- the cw funciton should be changed to
bool cw(...)
{
...
... < - EPSILON
}
because it is wrong for 0.0 .
(*) Page 317-318 -- convex_hull code.
Change the loop contents to:
while (i <= n) {
if (cw(hull->p[top-1], hull->p[top], in[i]))
top = top-1; /* top not on hull */
else {
if (!collinear(hull->p[top - 1], hull->p[top], in[i]))
top = top+1;
copy_point(in[i],hull->p[top]);
i = i+1;
}
}
(*) Page 319 function sort_and_remove_duplicates --
The condition of the for-loop should be i=3$ should be $n >= 4$.
(*) Page 324, second paragraph -- the references to "p" in this
paragraph should be to the polygon $P$.
(*) Page 325 Last paragraph, starts with "As another example, consider a rectangle...."
B(P) = 2 | y[2] - y[1] + 1 | + 2 | x[2] - x[1] + 1 | - 4 = 2(dy - dx) should be
B(P) = 2( | y[2] - y[1] | + 1 ) + 2( | x[2] - x[1] | + 1 ) - 4 = 2(dy + dx)
and
I(P) = (dx+1)(dy+1) - 2(dy - dx) should be
I(P) = (dx+1)(dy+1) - 2(dy + dx)
Page 333, line 8, last word -- "an object" should be "a dot"
(*) Page 333 14.7.6 Radar Tracking, Output --
Add "Sort output by ascending angle value and then by descending distance value".
This is not specified in the book but it is on the uva website.
Page 342, line -2: "absence" should be "presence"
Page 347, line 3 -- ACM ICPC rules have changed, and first-year
graduate students are only allowed if it has been at most five years
since you started your undergradate program. Of course, we will be happy
to have you for graduate study at Stony Brook even if you are not eligible
for the team!
Page 348, 110502 "Reverse and Add" -- authors name should be Enrique, not Erick
Page 348, 110701 "Light, More Light" -- the list of authors should be:
"S. M. Mahbub Mrushed (Udvranto Pathik), Sadi Khan"
Page 348, problem 110302 "Where's Waldorf" -- Add credit for the problem
to the University of Waterloo Computer Science Club (UWCSC)
Page 349, problem 111308 "How Big is It" -- Add credit for the problem
to the University of Waterloo Computer Science Club (UWCSC)
(*) Page 349, problem 111203 "Star" -- Martins Opmanis is the
real author of this problem, which appeared in the 4th Baltic Olympiad in
Informatics, held in Tartu(Estonia) in April 25-28, 1998.