Tag Archives: pointer
C++ || Snippet – Custom “Shuffle” Function For Arrays
The following is a custom “Shuffle” function which shuffles the contents of an array. This function rearranges each item within the array by swapping the value of a given item with that of some other randomly selected item.
The code demonstrated on this page is different from the STL random_shuffle function in that this implementation is meant to work mainly on standard arrays.
This implementation revolves around using a series of void pointers.
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// ============================================================================ // Author: K Perkins // Date: July 17, 2013 // Taken From: http://programmingnotes.org/ // File: Shuffle.cpp // Description: Demonstrates the use of a custom "Shuffle" function // which rearranges/shuffles the contents of an array. // ============================================================================ #include <iostream> #include <ctime> #include <cstdlib> #include <cstring> #include <string> using namespace std; // function prototype void Shuffle(const void* arry, int arrySize, size_t sizeType); int main() { // declare variables char charArry[] = "This is a simple C-String"; char* twoD_CharArry[] = {"This","is","a","2-D","C-String","array"}; int intArry[] = {1,2,3,4,5,6,7,8,9,10}; string str = "This is a simple std::string"; string strArry[] = {"This","is","a","std::string","array"}; // char array Shuffle(charArry, strlen(charArry), sizeof(char)); cout<<charArry<<endl<<endl; // int array Shuffle(intArry, 10, sizeof(int)); for(int x = 0; x < 10; ++x) { cout<<intArry[x]<<" "; } cout<<endl<<endl; // 2-D char array Shuffle(twoD_CharArry, 6, sizeof(char*)); for(int x = 0; x < 6; ++x) { cout<<twoD_CharArry[x]<<" "; } cout<<endl<<endl; // std::string Shuffle(str.c_str(), str.length(), sizeof(char)); cout<<str<<endl<<endl; // std::string array Shuffle(strArry, 5, sizeof(string)); for(int x = 0; x < 5; ++x) { cout<<strArry[x]<<" "; } cout<<endl<<endl; return 0; }// end of main /** * FUNCTION: Shuffle * USE: Rearranges each item within the array by swapping the value of a given * item with that of some other randomly selected item * @param arry - the array being shuffled * @param arrySize - the total number of items in the array (the array length) * @param sizeType - the number of bytes required to represent the data-type * of the individual items in the array * @return - the shuffled array */ void Shuffle(const void* arry, int arrySize, size_t sizeType) { srand(time(NULL)); for(unsigned x = 0; x < (unsigned)arrySize; ++x) { int r = rand() % arrySize; // get the value of two items in the array void* a = ((char*)arry)+(x*sizeType); void* b = ((char*)arry)+(r*sizeType); // swap the value of the two items void* tmp = malloc(sizeType); memcpy(tmp, a, sizeType); memcpy(a, b, sizeType); memcpy(b, tmp, sizeType); free(tmp); } }// http://programmingnotes.org/ |
QUICK NOTES:
The highlighted lines are sections of interest to look out for.
The code is heavily commented, so no further insight is necessary. If you have any questions, feel free to leave a comment below.
Once compiled, you should get this as your output
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sesnisai g S-tmirp TlhiC 2 5 6 4 10 9 1 8 3 7 C-String array a 2-D is This i:gdsmsa: i ilnptti es Trshs is array std::string This a |
C++ || Snippet – Custom “For Each” Iterator Function For Arrays
A “For Each” algorithm is a function that iterates over all the elements contained in a storage collection, and calls a separate user defined function to manipulate each element within that collection.
The code demonstrated on this page is different from the STL for_each function in that this implementation is meant to work mainly on standard arrays.
The example below illustrates the “For Each” concept in a fully compilable and working demonstration. This example is trivial in that all it does is call a separate user defined function to display all of the contents within each array. This implementation revolves around using a simple function pointer and a series of void pointers.
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// ============================================================================ // Author: K Perkins // Date: July 12, 2013 // Taken From: http://programmingnotes.org/ // File: ForEach.cpp // Description: Demonstrates the use of a custom "For Each" function // implementation. // ============================================================================ #include <iostream> #include <cstring> #include <string> using namespace std; // function prototypes void ForEach(const void* arry, int arrySize, size_t sizeType, void(*function)(void*)); void PrintChar(void* c); // user defined functions void PrintInt(void* c); void PrintCString(void* c); void PrintString(void* c); int main() { // declare variables char charArry[] = "This is a simple C-String"; char* twoD_CharArry[] = {"This","is","a","2-D","C-String","array"}; int intArry[] = {1,2,3,4,5,6,7,8,9,10}; string str = "This is a simple std::string"; string strArry[] = {"This","is","a","std::string","array"}; // char array ForEach(charArry, strlen(charArry), sizeof(char), PrintChar); cout<<endl<<endl; // int array ForEach(intArry, 10, sizeof(int), PrintInt); cout<<endl<<endl; // 2-D char array ForEach(twoD_CharArry, 6, sizeof(char*), PrintCString); cout<<endl<<endl; // std::string ForEach(str.c_str(), str.length(), sizeof(char), PrintChar); cout<<endl<<endl; // std::string array ForEach(strArry, 5, sizeof(string), PrintString); cout<<endl<<endl; return 0; }// end of main /** * FUNCTION: ForEach * USE: Applies the "void(*function)" to each of the elements in the array * @param arry - the array being iterated * @param arrySize - the total number of items in the array (the array length) * @param sizeType - the number of bytes required to represent the data-type * of the individual items in the array * @param *function - function pointer that accepts an element in the array as argument * @return - none */ void ForEach(const void* arry, int arrySize, size_t sizeType, void(*function)(void*)) { for(unsigned x = 0; x < (unsigned)arrySize; ++x) { function((char*)arry + (x*sizeType)); } }// end of ForEach void PrintChar(void* c) { cout<<*(char*)c <<" "; }// end of PrintChar void PrintInt(void* c) { cout<<*(int*)c <<" "; }// end of PrintInt void PrintCString(void* c) { cout<<*(char**)c <<" "; }// end of PrintCString void PrintString(void* c) { cout<<*(string*)c <<" "; }// http://programmingnotes.org/ |
QUICK NOTES:
The highlighted lines are sections of interest to look out for.
The code is heavily commented, so no further insight is necessary. If you have any questions, feel free to leave a comment below.
Once compiled, you should get this as your output
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T h i s i s a s i m p l e C - S t r i n g 1 2 3 4 5 6 7 8 9 10 This is a 2-D C-String array T h i s i s a s i m p l e s t d : : s t r i n g This is a std::string array |
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