Java实现常见排序算法详解-优快云博客

本文链接：https://blog.youkuaiyun.com/m0_52846268/article/details/121591485

本文详细介绍了Java中选择排序、插入排序、归并排序、快速排序和堆排序的实现，涵盖了不同类型的排序算法，有助于理解与应用。

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选择排序

代码实现：

public class SelectionSort {

    /**
     * 选择排序
     *
     * @param arr
     */
    public static void sort(int arr[]) {
        /********** Begin *********/
        for(int i = 0;i < arr.length - 1;i++){
            for(int j = i+1;j < arr.length;j++){
                if(arr[i] > arr[j]){
                    int temp = arr[i];
                    arr[i] = arr[j];
                    arr[j] = temp;
                }
            }
            print(arr);
        }
        

        /********** End *********/
    }

    private static void print(int arr[]) {
        for (int i = 0; i < arr.length; i++) {
            System.out.print(arr[i] + " ");
        }
        System.out.println();
    }

}

插入排序

public class InsertionSort {

    public static void sort(int arr[]) {
        /********** Begin *********/
        for (int i = 1;i < arr.length;i++){
            int value = arr[i];
            int index = i - 1;
            while (index >= 0 && value < arr[index]){
                arr[index+1] = arr[index];
                index--;
            }
            if (index+1 != i)
                arr[index + 1] = value;
            print(arr);
        }
        /********** End *********/
    }

    private static void print(int arr[]) {
        for (int i = 0; i < arr.length; i++) {
            System.out.print(arr[i] + " ");
        }
        System.out.println();
    }
}

归并排序

public class MergeSort {

    /**
     * lo, hi都是指下标
     */
    public static void sort(int arr[], int lo, int hi) {
        if (lo < hi) {
            int mid = (lo + hi) / 2;
            sort(arr, lo, mid);
            sort(arr, mid + 1, hi);
            merge(arr, lo, mid, hi);
            print(arr);
        }
    }

    private static void merge(int arr[], int p, int q, int r) {
        /********** Begin *********/
        int[] temp = new int[r-p+1];
        int i = p;
        int j = q+1;
        int k = 0;
        while (i<= q && j<= r){
            if(arr[i]<arr[j]){
                temp[k++] = arr[i++];
            }else{
                temp[k++] = arr[j++];
            }
        }
        while(i<=q){
            temp[k++] = arr[i++];
        }
        while(j<=r){
            temp[k++] = arr[j++];
        }
        for(int x=0;x<temp.length;x++){
            arr[x+p] = temp[x];
        }
        /********** End *********/
    }

    private static void print(int arr[]) {
        for (int i = 0; i < arr.length; i++) {
            System.out.print(arr[i] + " ");
        }
        System.out.println();
    }
}

快速排序

public class QuickSort {

    public void sort(int arr[], int low, int high) {
        /********** Begin *********/
        int i = low;
        int j = high + 1;
        int povit = arr[low];
        while (i < j) {
            while (j > low && arr[--j] >= povit) ;
            while (i < high && arr[++i] <= povit) ;
            if (i>=j)break;
            int temp = arr[j];
            arr[j] = arr[i];
            arr[i] = temp;
            print(arr);
        }
        int temp = arr[j];
        arr[j] = arr[low];
        arr[low] = temp;
        print(arr);
        if (i > low) sort(arr, low, j - 1);
        if (j < high) sort(arr, j + 1, high);
        /********** End *********/
    }


    private static void print(int arr[]) {
        for (int i = 0; i < arr.length; i++) {
            System.out.print(arr[i] + " ");
        }
        System.out.println();
    }
}

堆排序

public class HeapSort {

    public static void sort(int arr[]) {
        /********** Begin *********/
        int parent = 0;
        int temp = 0;
        for (int i = (arr.length - 1) / 2; i >= 0; i--) {
            parent = i;
            temp = arr[parent];
            int lChild = 2 * parent + 1;
            while (lChild < arr.length) {
                int rChild = lChild + 1;
                if (rChild < arr.length && arr[lChild] < arr[rChild]) lChild++;
                if (temp >= arr[lChild]) break;
                arr[parent] = arr[lChild];
                parent = lChild;
                lChild = 2 * lChild + 1;
            }
            arr[parent] = temp;
        }
        for (int i = arr.length - 1; i > 0; i--) {
            temp = arr[i];
            arr[i] = arr[0];
            arr[0] = temp;
            parent = 0;
            temp = arr[parent];
            int lChild = 2 * parent + 1;
            while (lChild < i) {
                int rChild = lChild + 1;
                if (rChild < i && arr[lChild] < arr[rChild]) lChild++;
                if (temp >= arr[lChild]) break;
                arr[parent] = arr[lChild];
                parent = lChild;
                lChild = 2 * lChild + 1;
            }
            arr[parent] = temp;
            print(arr);
        }
        /********** End *********/
    }

    private static void print(int[] arr) {
        for (int i = 0; i < arr.length; i++) {
            System.out.print(arr[i] + " ");
        }
        System.out.println();
    }

}