Notebook

This is a variation of selection sort, it bring the largest pancake not yet sorted to the top with one flip; take it down to its final position with one more flip; and repeat this process for the remaining pancakes. The algorithm has been discussed in following wiki link: Pancake Sorting The algorithm is visually represented in following link: Pancake Sorting(Visualization) The idea of this sorting is similar to Selection Sort, here taking maximum items one by one and started placing those from last and at the same time reducing the vector size one by one. To place bigger items in order from last using flips two move to their respective positions. Here is the implementation using std::rotate() and std::reverse(). The output: 

This is an effort to implement insertion sort in C++ way using Standard Template Library. The below implementation is for vector of any type. Two STL libraries algorithm has been used. 1. std::lower_bound 2. std::rotate The implementation cross compiler compatible, tested on GNU C++ (5.4.0) and Microsoft C++ (2010). //g++  5.4.0 #include < iostream > #include < algorithm > #include < vector > template< typename T > void insertionSort(std::vector< T > &vec) { typedef typename std::vector< T >::value_type vt; typename std::vector< vt >::iterator itBegin = vec.begin(); typename std::vector< vt >::iterator itEnd = vec.end(); for(typename std::vector< vt >::iterator it = itBegin; it != itEnd; ++it) { typename std::vector ::iterator ins = std::lower_bound(itBegin, it, *it); std::rotate(ins, it, std::next(it)); } } int main() {     int arr[] = {34, 20, 99, 10, 23}; std::vector< int > v(s

In my last article have seen how we can leverage C++ STL to do selection sort on the vector of integers only. However, the selection sort wasn't very generic to accept vectors of any basic type and sort accordingly. The below program was an effort to make the same selection sort (ascending order) implementation for vectors of any type like vectors of integers, doubles, chars, etc. #include < iostream > #include < algorithm > #include < vector > template < class ForwardIterator1, class ForwardIterator2 > void iters_swap (ForwardIterator1 a, ForwardIterator2 b) {     std::swap (*a, *b); } template < typename T > void selectionSort(std::vector< T > &v) { // Selection sort typedef typename std::vector ::value_type vt; typename std::vector ::iterator it = v.begin(); while(it != v.end()) {     typename std::vector ::iterator i_Min = std::min_element (it, v.end()); iters_swap(i_Min, it); ++it; } } int main() {

Selection Sort using Standard Template Libraries (not C++ 11): Selection sort works by finding smallest element from the list unsorted list, swap with leftmost element and proceed until all the elements are in order. Selecting the lowest element requires scanning all n elements (this takes n − 1 comparisons) and then swapping it into the first position. Finding the next lowest element requires scanning the remaining n − 1 elements and so on. Hence the complexity is  O(N^2) . The C++ implementation is like below: #include < iostream > #include < algorithm > #include < vector > template < class ForwardIterator1, class ForwardIterator2 > void iters_swap (ForwardIterator1 a, ForwardIterator2 b) {      std::swap (*a, *b); } template < typename T > void selectionSort(T &v) { // Selection sort std::vector ::iterator it = v.begin(); while(it != v.end()) {         std::vector ::iterator i_Min = std::min_element(it,

A scenario, as per C++ specification supported and also supported by the GNU C++ compiler but not right to do so. Example: The following piece of code works both in the GNU C++ compiler as well as Microsoft C++ compiler. Code execution gives the right result (I mean expected output). #include  < vector > #include < iostream > class Simple { public: Simple(unsigned int aInt) : memberInteger(aInt) { } void Amaze() { myVector = { Simple(1), Simple(2) }; } unsigned int memberInteger; std::vector < Simple > myVector; }; int main() { Simple s(0); s.Amaze(); size_t sz = s.myVector.size(); return 0; } The size of my vector returns 2. Now, I've changed the a code little bit and it gets compiled well in Gnu C++ compiler(4.9.2 and used "g++ -std=c++11 -Wall Simple_Defeat.cpp -o Simple_Defeat" to compile) but not in Microsoft C++ compiler (Checked with 2013): #include < vector > #include < iostream &g

A thread cleanup handler in Linux and Windows thread cancellation: A cleanup handler is a measure, used to deallocate a resource only if the thread exits or canceled. To register a cleanup handler, need to call pthread_cleanup_push() and pass a pointer to cleanup function and the void * argument. The pthread_cleanup_pop() function removes the routine at the top of the calling thread's cancellation cleanup stack and optionally invokes it (if execute is non-zero). The following sample code shows how a dynamically allocated buffer from a thread can be deallocated on canceling the thread in Linux. #include < pthread.h > #include < stdio.h > #include < string.h > #include < unistd.h >  char *pgArray = 0; /* Buffer allocation */ char * allocate_array (size_t size) {     return new char[size]; } void release_array (void *pArg) {     if(pgArray)     {         printf("release_array() called..\n");         delete []pgArray;     }

Thread Cancellation in GNU/Linux : Today, I'm interested to explore how we can prepare thread in GNU/Linux to ignore thread cancellation. This is acvhieved with pthread_setcancelstate(). The signature of the function is: int pthread_setcancelstate(int state, int *oldstate);  The function is thread and signal safe. The function sets the cancel  state to one of PTHREAD_CANCEL_ENABLE or  PTHREAD_CANCEL_DISABLE and returns the old cancel state. Please see the second parameter. void *Print_Details(void *param) {      printf("This is secondary thread's entry...\n");      int oldState;      pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &oldState);      sleep(1);      for(int i = 0; i < 10; ++i)      {           printf("Inside the secondary thread...\n");      }      pthread_setcancelstate(oldState, NULL);      printf("This is secondary thread's exit...\n");      return NULL; } /* Main program */ int main() {      pt