Recursively quick Sort - C++ Data Structure

C++ examples for Data Structure:Sort

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Description

Recursively quick Sort

Demo Code

#include <iomanip>
#include <iostream>
#include <utility>

void quickSort(int[], int, int);
int partition(int[], int, int);
void swap(int*, int*);
void printArray(int[], int);

int main(int argc, const char* argv[]) {
    const int limit = 10;

    int a[limit] = {32, 12, 6, 124, 829, 8, 120, 122, 628, 425};

    std::cout << "Unsorted Array:" << std::endl;

    printArray(a, limit);// w  ww  .  j  a  v  a 2s .c  o m

    quickSort(a, 0, limit - 1);

    std::cout << "\nSorted Array:" << std::endl;

    printArray(a, limit);

    return 0;
}

void quickSort(int a[], int start, int end) {
    // base case
    if (start < end) {
        // middle = subscript of sorted element
        int pivot = partition(a, start, end);

        // sort beginning
        quickSort(a, start, pivot - 1);
        // sort end
        quickSort(a, pivot + 1, end);
    }
}
// takes first element as pivot, sorts array around it's value
// Returns subscript of sorted element.
int partition(int a[], int start, int end) {
    int pivot = a[start];  // value of pivot
    int wi = start;        // working index ()

    // loop through unsorted array
    for (int j = start + 1; j <= end; ++j) {
        if (a[j] <= pivot) {
            ++wi;
            swap(&a[j], &a[wi]);
        }
    }
    swap(&a[wi], &a[start]);

    return wi;
}
void swap(int* a, int* b) {
    int temp = *a;
    *a = *b;
    *b = temp;
}
void printArray(int a[], int limit) {
    for (int i = 0; i < limit; ++i) {
        std::cout << std::setw(4) << a[i];
    }

    std::cout << std::endl;
}

Result


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