How to Use Quick Sort Function in C++ in the Array of Integers
"Quick sort" is a sorting algorithm that runs in n * log(n) time, which makes it very efficient for sorting large data sets. It uses a divide-and-conquer approach that efficiently splits data sets to work on multiple components simultaneously. The C++ standard library provides a function that implements the quick sort algorithm. Sorting a list of integers with quick sort is straightforward when using this standard library implementation of the algorithm.
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Instructions
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Include the standard library header "stdlib.h". This header contains the quick sort implementation, which is accessed by calling the function "qsort":
#include <stdlib.h>
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Create your comparison function. The comparison function accepts two arguments of type "void *", which must be cast to a specific data type and then compared. If the first element is less than the second, a negative value must be returned from this function. If the first element is greater than the second, return a positive value. If both elements are equal, return zero:
int CompareIntegers( const void * arg1, const void * arg2)
{
int val1 = *(int *) arg1;
int val2 = *(int *) arg2;
if(val1 < val2)
{
return -1;
}
else if(val1 > val2)
{
return 1;
}
// if we got here, both elements are equal
return 0;
}
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In your code, call the qsort function. The qsort function takes four arguments: a pointer to the array to sort, the number of elements in the array, the size of each element in the array, and the comparison function.
// sort the array of integers
qsort( arrayToSort, numberOfElements, sizeof(int), CompareIntegers );
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Tips & Warnings
The comparison function can be modified to take any type of data. Use this feature to sort arrays of structs, classes, or any object you can code.
The qsort function can also be used with STL containers. It is not strictly necessary to use dynamic arrays.
Ensure that the array to be sorted has been properly initialized and filled with values. An improperly created array can result in null reference exceptions.
Ensure that the element count provided to the qsort function is accurate. An inaccurate value can result in either a partially unsorted array or a segmentation fault.
Ensure that the element size provided to qsort is accurate. An inaccurate element size can lead to memory corruption and segmentation faults.
