Check if a string is palindrome

by

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

More Related Contents:

  1. how to find month of quarter not a quarter of month [closed]
  2. Increment in both side in C [closed]
  3. Why can templates only be implemented in the header file?
  4. Calling C/C++ from Python? [closed]
  5. How do I print out the contents of a vector?
  6. Remove elements of a vector inside the loop
  7. Why does optimisation kill this function?
  8. Strict aliasing rule and ‘char *’ pointers
  9. Automatically stop Visual C++ 2008 build at first compile error?
  10. When can I use explicit operator bool without a cast?
  11. When is a C++ destructor called?
  12. How to project a point onto a plane in 3D?
  13. Is std::string ref-counted in GCC 4.x / C++11?
  14. What is the idiomatic way in CMAKE to add the -fPIC compiler option?
  15. Is f(void) deprecated in modern C and C++? [duplicate]
  16. Does “std::size_t” make sense in C++?
  17. GNU C++ how to check when -std=c++0x is in effect?
  18. Is it possible to use dynamic name for variables in c++
  19. Why is NVIDIA Pascal GPUs slow on running CUDA Kernels when using cudaMallocManaged
  20. run a program with more than one source files in GNU c++ compiler
  21. std::thread error (thread not member of std)
  22. C++: Why pass-by-value is generally more efficient than pass-by-reference for built-in (i.e., C-like) types
  23. behavior of const_cast in C++ [duplicate]
  24. The proper way of forcing a 32-bit compile using CMake
  25. When did C++ compilers start considering more than two hex digits in string literal character escapes?
  26. Linking C++ code with ‘gcc’ (without g++)
  27. When will ofstream::open fail?
  28. What standard clause mandates this lvalue-to-rvalue conversion?
  29. How is this a most vexing parse?
  30. What does the vertical bar ( | ) mean in C++?

Leave a Comment