School-Coding-Cpp/array/arraytools.h

/*
AUTORE: Manuel Vichi
Array Tools
*/
#include <iostream>
#include <array>
#include <vector>
#include <cstdlib>
using namespace std;
void insertionSort(int arr[], int n)
{
    for (int i = 1; i < n; ++i) {
        int key = arr[i];
        int j = i - 1;

        /* Move elements of arr[0..i-1], that are
           greater than key, to one position ahead
           of their current position */
        while (j >= 0 && arr[j] > key) {
            arr[j + 1] = arr[j];
            j = j - 1;
        }
        arr[j + 1] = key;
    }
}
vector<int> countSort(vector<int>& inputArray)
{

    int N = inputArray.size();

    // Finding the maximum element of array inputArray[].
    int M = 0;

    for (int i = 0; i < N; i++)
        M = max(M, inputArray[i]);

    // Initializing countArray[] with 0
    vector<int> countArray(M + 1, 0);

    // Mapping each element of inputArray[] as an index
    // of countArray[] array

    for (int i = 0; i < N; i++)
        countArray[inputArray[i]]++;

    // Calculating prefix sum at every index
    // of array countArray[]
    for (int i = 1; i <= M; i++)
        countArray[i] += countArray[i - 1];

    // Creating outputArray[] from countArray[] array
    vector<int> outputArray(N);

    for (int i = N - 1; i >= 0; i--)

    {
        outputArray[countArray[inputArray[i]] - 1]
            = inputArray[i];

        countArray[inputArray[i]]--;
    }

    return outputArray;
}
void selectionSort(vector<int> &arr) {
    int n = arr.size();

    for (int i = 0; i < n - 1; ++i) {

        // Assume the current position holds
        // the minimum element
        int min_idx = i;

        // Iterate through the unsorted portion
        // to find the actual minimum
        for (int j = i + 1; j < n; ++j) {
            if (arr[j] < arr[min_idx]) {

                // Update min_idx if a smaller
                // element is found
                min_idx = j; 
            }
        }

        // Move minimum element to its
        // correct position
        swap(arr[i], arr[min_idx]);
    }
}
int partition(vector<int>& arr, int low, int high) {
  
    // Choose the pivot
    int pivot = arr[high];
  
    // Index of smaller element and indicates 
    // the right position of pivot found so far
    int i = low - 1;

    // Traverse arr[;ow..high] and move all smaller
    // elements on left side. Elements from low to 
    // i are smaller after every iteration
    for (int j = low; j <= high - 1; j++) {
        if (arr[j] < pivot) {
            i++;
            swap(arr[i], arr[j]);
        }
    }
    
    // Move pivot after smaller elements and
    // return its position
    swap(arr[i + 1], arr[high]);  
    return i + 1;
}

// The QuickSort function implementation
void quickSort(vector<int>& arr, int low, int high) {
  
    if (low < high) {
      
        // pi is the partition return index of pivot
        int pi = partition(arr, low, high);

        // Recursion calls for smaller elements
        // and greater or equals elements
        quickSort(arr, low, pi - 1);
        quickSort(arr, pi + 1, high);
    }
}
void bubbleSort(vector<int>& arr) {
    int n = arr.size();
    bool swapped;
  
    for (int i = 0; i < n - 1; i++) {
        swapped = false;
        for (int j = 0; j < n - i - 1; j++) {
            if (arr[j] > arr[j + 1]) {
                swap(arr[j], arr[j + 1]);
                swapped = true;
            }
        }
      
        // If no two elements were swapped, then break
        if (!swapped)
            break;
    }
}
void CocktailSort(int a[], int n)
{
    bool swapped = true;
    int start = 0;
    int end = n - 1;
 
    while (swapped) {
        // reset the swapped flag on entering
        // the loop, because it might be true from
        // a previous iteration.
        swapped = false;
 
        // loop from left to right same as
        // the bubble sort
        for (int i = start; i < end; ++i) {
            if (a[i] > a[i + 1]) {
                swap(a[i], a[i + 1]);
                swapped = true;
            }
        }
 
        // if nothing moved, then array is sorted.
        if (!swapped)
            break;
 
        // otherwise, reset the swapped flag so that it
        // can be used in the next stage
        swapped = false;
 
        // move the end point back by one, because
        // item at the end is in its rightful spot
        --end;
 
        // from right to left, doing the
        // same comparison as in the previous stage
        for (int i = end - 1; i >= start; --i) {
            if (a[i] > a[i + 1]) {
                swap(a[i], a[i + 1]);
                swapped = true;
            }
        }
 
        // increase the starting point, because
        // the last stage would have moved the next
        // smallest number to its rightful spot.
        ++start;
    }
}
void printArray(int a[], int n)
{
    for (int i = 0; i < n; i++)
        printf("%d ", a[i]);
    printf("\n");
}