Sorting Algorithms

 1. Bubble sort.

public static int bubble3(int[] arr) {
    boolean swapped;
    int count = 0;
    int n = arr.length;
    for (int i = 0; i < n - 1; i++) {
        swapped = false;
        for (int j = 0; j < n - i - 1; j++) {
            count++;
            if (arr[j] > arr[j + 1]) {
                swapped = true;
                int temp = arr[j];
                arr[j] = arr[j + 1];
                arr[j + 1] = temp;
            }
        }
        if (!swapped) break;
    }
    return count;
}

2. Selection sort.

public static int selectionSort1(int[] arr) {
    int count = 0;
    int n = arr.length;
    for (int i = 0; i < n - 1; i++) {
        int min = i;
        for (int j = i + 1; j < n; j++) {
            count++;
            if (arr[j] < arr[min]) {
                min = j;
            }
        }
        if (min != i) {
            int temp = arr[i];
            arr[i] = arr[min];
            arr[min] = temp;
        }
    }
    return count;
}

improved version:

public static int selectionSort2(int[] arr) {
    int count = 0;
    int n = arr.length;
    for (int i = 0; i < n - 1; i++) {
        int min = i;
        for (int j = i; j < n; j++) {
            count++;
            if (arr[j] < arr[min]) {
                min = j;
            }
        }
        if (min != i) {
            int temp = arr[i];
            arr[i] = arr[min];
            arr[min] = temp;
        } else {
            break;
        }
    }
    return count;
}

3. Insertion sort

public static void insertionSort(int[] arr) {
    int n = arr.length;
    for (int i = 1; i < n; i++) {
        int temp = arr[i];
        int j = i;
        while (j > 0 && arr[j - 1] > temp) {
            arr[j] = arr[j - 1];
            j--;
        }
        arr[j] = temp;
    }
}

public static void insertionSort(int[] arr) {
    int n = arr.length;
    for (int i = 0; i < n - 1; i++) {
        for (int j = i + 1; j > 0; j--) {
            if (arr[j] < arr[j - 1]) {
                int temp = arr[j];
                arr[j] = arr[j - 1];
                arr[j - 1] = temp;
            } else {
                break;
            }
        }
    }
}

4. Counting sort:

#include <iomanip>
#include <iostream>
#include <vector>

using namespace std;
using namespace std;

void countingSortPositiveArray(int a[], int n) {
    int max = INT_MIN;
    int min = INT_MAX;
    int range;

    // step 1: find max and min values for defining range
    for (int i = 0; i < n; i++) {
        if (a[i] > max) {
            max = a[i];
        }
        if (a[i] < min) {
            min = a[i];
        }
    }
    range = max - min + 1;

    // step 2: initialize count array
    int count[range];
    for (int i = 0; i < range; i++) {
        count[i] = 0;
    }
    for (int i = 0; i < n; i++) {
        count[a[i]]++;
    }


    // step 3: update count array
    for (int i = 1; i <= range; i++) {
        count[i] = count[i] + count[i - 1];
    }

    // step 4: initialize result array
    int b[n];
    for (int i = n - 1; i >= 0; i--) {
        b[--count[a[i]]] = a[i];
    }
    for (int i = 0; i < n; i++) {
        cout << b[i] << " ";
    }
}

void countingSortNegativeArray(int a[], int n) {
    int max = INT_MIN;
    int min = INT_MAX;
    int range;

    // step 1: find max and min values for defining range
    for (int i = 0; i < n; i++) {
        if (a[i] > max) {
            max = a[i];
        }
        if (a[i] < min) {
            min = a[i];
        }
    }
    range = max - min + 1;

    // step 2: initialize count array
    int count[range];
    for (int i = 0; i < range; i++) {
        count[i] = 0;
    }

    // offset each element
    for (int i = 0; i < n; i++) {
        count[a[i] - min]++;
    }

    // step 3: update count array
    for (int i = 1; i <= range; i++) {
        count[i] = count[i] + count[i - 1];
    }

    // step 4: initialize result array
    int b[n];
    for (int i = n - 1; i >= 0; i--) {
        b[--count[a[i] - min]] = a[i];
    }
    for (int i = 0; i < n; i++) {
        cout << b[i] << " ";
    }
}

int main() {
    int arr[] = {2, 1, 1, 0, 2, 5, 4, 0, 2, 8, 7, 7, 9, 2, 0, 1, 9};
    countingSortPositiveArray(arr, 17);
    cout << endl;

    int arr2[] = {3, 7, 0, -3, 9, 7, 0, 1, 4};
    countingSortNegativeArray(arr2, 9);
}