I need to create a program that allows a user to input a string and my program will check to see if that string they entered is a palindrome (word that can be read the same backwards as it can forwards).
This question is related to
c++
bool IsPalindrome(const char* psz)
{
int i = 0;
int j;
if ((psz == NULL) || (psz[0] == '\0'))
{
return false;
}
j = strlen(psz) - 1;
while (i < j)
{
if (psz[i] != psz[j])
{
return false;
}
i++;
j--;
}
return true;
}
// STL string version:
bool IsPalindrome(const string& str)
{
if (str.empty())
return false;
int i = 0; // first characters
int j = str.length() - 1; // last character
while (i < j)
{
if (str[i] != str[j])
{
return false;
}
i++;
j--;
}
return true;
}
// The below C++ function checks for a palindrome and
// returns true if it is a palindrome and returns false otherwise
bool checkPalindrome ( string s )
{
// This calculates the length of the string
int n = s.length();
// the for loop iterates until the first half of the string
// and checks first element with the last element,
// second element with second last element and so on.
// if those two characters are not same, hence we return false because
// this string is not a palindrome
for ( int i = 0; i <= n/2; i++ )
{
if ( s[i] != s[n-1-i] )
return false;
}
// if the above for loop executes completely ,
// this implies that the string is palindrome,
// hence we return true and exit
return true;
}
I'm no c++ guy, but you should be able to get the gist from this.
public static string Reverse(string s) {
if (s == null || s.Length < 2) {
return s;
}
int length = s.Length;
int loop = (length >> 1) + 1;
int j;
char[] chars = new char[length];
for (int i = 0; i < loop; i++) {
j = length - i - 1;
chars[i] = s[j];
chars[j] = s[i];
}
return new string(chars);
}
Reverse the string and check if original string and reverse are same or not
Note that reversing the whole string (either with the rbegin()
/rend()
range constructor or with std::reverse
) and comparing it with the input would perform unnecessary work.
It's sufficient to compare the first half of the string with the latter half, in reverse:
#include <string>
#include <algorithm>
#include <iostream>
int main()
{
std::string s;
std::cin >> s;
if( equal(s.begin(), s.begin() + s.size()/2, s.rbegin()) )
std::cout << "is a palindrome.\n";
else
std::cout << "is NOT a palindrome.\n";
}
demo: http://ideone.com/mq8qK
Source: Stackoverflow.com