Quick sort on vector - C++ STL

C++ examples for STL:vector

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Description

Quick sort on vector

Demo Code

#include <cstdlib>
#include <iostream>
#include <vector>
#include <ctime>
template <typename T>
void printVector(const std::vector<T>& data) {
    for (T elem : data) std::cout << elem << " ";

    std::cout << std::endl;//from w w  w. ja  v a 2 s. com
}

void quickSortHelper(std::vector<int>&, int, int);
int partition(std::vector<int>&, int, int);

int main(int argc, const char* argv[]) {
    std::srand(time(0));

    const int limit = 100;
    const int size = 100;
    std::vector<int> intVec;

    for (int i = 0; i < size; ++i) intVec.push_back(((rand() % limit) + 1));

    std::cout << "Unsorted Vector:\n";
    printVector(intVec);

    quickSortHelper(intVec, 0, (intVec.size() - 1));

    std::cout << "\nAfter Sorting:\n";
    printVector(intVec);

    return 0;
}
// Recursive quick sort
void quickSortHelper(std::vector<int>& intVec, int left, int right) {
    int index = partition(intVec, left, right);

    if (left < index - 1)
        quickSortHelper(intVec, left, index - 1);

    if (index < right)
        quickSortHelper(intVec, index, right);
}
// partition
int partition(std::vector<int>& intVec, int left, int right) {
    // pick pivot in middle of vector
    int pivot = intVec[(left + right) / 2];

    while (left <= right) {
        // find element on the left
        // that should be on right
        while (intVec[left] < pivot) ++left;

        // find element on right
        // that should be on left
        while (intVec[right] > pivot) --right;

        if (left <= right) {
            std::swap(intVec[left], intVec[right]);
            ++left;
            --right;
        }
    }
    return left;
}

Result


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