Write a recursive algorithm to determine if a string is a palindrome. Your
algorithm should accept as an input parameter a const char * array
containing the suspected palindrome and return true if the input really is a
palindrome; otherwise it should return false. Your function may contain any
other parameters you think necessary. You need not write in c++, but you must
show a recursive algorithm.
If the string cstrc is a palindrome, then so is the string
str; this is the basis for a recursive test for palindromes. If str
is less than two characters long, then str is also a palindrome; this is
the stopping condition.
From these two observations, it's a short hop to some recursive code to find palindromes:
bool palindrome(const char str[])
return palindrome(str, str + strlen(a) - 1)
bool palindrome(const char * left, const char * right)
if (left >= right)
return true
else
return (*left == *right) and palindrome(f + 1, l - 1)
Most answers got close to the right answer, at least in the general details.
Some languages also provide a mapping in right-to-left order by decreasing negative index value.
Derive the expression to map indices to array elements for right-to-left order by decreasing negative index values. Don't forget to explain your derivation. Only answer the question for 1-dimensional arrays.
[]
and .at().
See Section 3.4, page 133, in Nyhoff.
This was a gimme, but there were only a few correct answers.
void time::add(unsigned delta) {
running_time += delta; // compilation error.
}
The following code compiles successfully:
int main() {
time t;
unsigned now;
now = t.running_time;
}
Show the declaration (not definition) of time.
(Here's a hint: this question has a correct answer.)
There's no access problem, because if main() can access
time::running_time, then time::add()() can certainly access it too.
The problem must be in the way time::running_time's being accessed:
main() accesses it for reading, but (time::add()) accesses it for writing,
which is causing problems.
class time {
public:
void add(unsigned delta);
const unsigned t.running_time;
};
Many answers to this weren't even close. If the question asks for a class definition, the answer should, at minimum, look something like a class definition.