Java实现的各种排序算法（包括冒泡，快排等）

Posted 2020-09-08

//堆排序   不稳定
import java.util.Arrays;

public class HeapSort {
    public static void main(String[] args) {
        int[] a={49,38,65,97,76,13,27,49,78,34,12,64};
        int arrayLength=a.length;  
        //循环建堆  
        for(int i=0;i<arrayLength-1;i++){  
            //建堆  
            buildMaxHeap(a,arrayLength-1-i);  
            //交换堆顶和最后一个元素  
            swap(a,0,arrayLength-1-i);  
            System.out.println(Arrays.toString(a));  
        }  
    }
    //对data数组从0到lastIndex建大顶堆
    public static void buildMaxHeap(int[] data, int lastIndex){
         //从lastIndex处节点（最后一个节点）的父节点开始 
        for(int i=(lastIndex-1)/2;i>=0;i--){
            //k保存正在判断的节点 
            int k=i;
            //如果当前k节点的子节点存在  
            while(k*2+1<=lastIndex){
                //k节点的左子节点的索引 
                int biggerIndex=2*k+1;
                //如果biggerIndex小于lastIndex，即biggerIndex+1代表的k节点的右子节点存在
                if(biggerIndex<lastIndex){  
                    //若果右子节点的值较大  
                    if(data[biggerIndex]<data[biggerIndex+1]){  
                        //biggerIndex总是记录较大子节点的索引  
                        biggerIndex++;  
                    }  
                }  
                //如果k节点的值小于其较大的子节点的值  
                if(data[k]<data[biggerIndex]){  
                    //交换他们  
                    swap(data,k,biggerIndex);  
                    //将biggerIndex赋予k，开始while循环的下一次循环，重新保证k节点的值大于其左右子节点的值  
                    k=biggerIndex;  
                }else{  
                    break;  
                }  
            }
        }
    }
    //交换
    private static void swap(int[] data, int i, int j) {  
        int tmp=data[i];  
        data[i]=data[j];  
        data[j]=tmp;  
    } 
}


//插入排序算法  稳定
public class InsertSort {

    public static void main(String[] args) {
        int[] a={49,38,65,97,76,13,27,49,78,34,12,64,1};
        System.out.println("排序之前：");
        for (int i = 0; i < a.length; i++) {
            System.out.print(a[i]+" ");
        }
        //直接插入排序
        for (int i = 1; i < a.length; i++) {
            //待插入元素
            int temp = a[i];
            int j;
            /*for (j = i-1; j>=0 && a[j]>temp; j--) {
                //将大于temp的往后移动一位
                a[j+1] = a[j];
            }*/
            for (j = i-1; j>=0; j--) {
                //将大于temp的往后移动一位
                if(a[j]>temp){
                    a[j+1] = a[j];
                }else{
                    break;
                }
            }
            a[j+1] = temp;
        }
        System.out.println();
        System.out.println("排序之后：");
        for (int i = 0; i < a.length; i++) {
            System.out.print(a[i]+" ");
        }
    }

}




// 归并排序  稳定
public class MergSort {
    public static void main(String[] args) {
        int[] a={49,38,65,97,76,13,27,49,78,34,12,64,1,8};
        System.out.println("排序之前：");
        for (int i = 0; i < a.length; i++) {
            System.out.print(a[i]+" ");
        }
        //归并排序
        mergeSort(a,0,a.length-1);
        System.out.println();
        System.out.println("排序之后：");
        for (int i = 0; i < a.length; i++) {
            System.out.print(a[i]+" ");
        }
    }

    private static void mergeSort(int[] a, int left, int right) {
        if(left<right){
            int middle = (left+right)/2;
            //对左边进行递归
            mergeSort(a, left, middle);
            //对右边进行递归
            mergeSort(a, middle+1, right);
            //合并
            merge(a,left,middle,right);
        }
    }

    private static void merge(int[] a, int left, int middle, int right) {
        int[] tmpArr = new int[a.length];
        int mid = middle+1; //右边的起始位置
        int tmp = left;
        int third = left;
        while(left<=middle && mid<=right){
            //从两个数组中选取较小的数放入中间数组
            if(a[left]<=a[mid]){
                tmpArr[third++] = a[left++];
            }else{
                tmpArr[third++] = a[mid++];
            }
        }
        //将剩余的部分放入中间数组
        while(left<=middle){
            tmpArr[third++] = a[left++];
        }
        while(mid<=right){
            tmpArr[third++] = a[mid++];
        }
        //将中间数组复制回原数组
        while(tmp<=right){
            a[tmp] = tmpArr[tmp++];
        }
    }
}




//冒泡排序   稳定
public class mp {
    public static void main(String[] args) {
        int[] a={49,38,65,97,76,13,27,49,78,34,12,64,1,8};
        System.out.println("排序之前：");
        for (int i = 0; i < a.length; i++) {
            System.out.print(a[i]+" ");
        }
        //冒泡排序
        for (int i = 0; i < a.length; i++) {
            for(int j = 0; j<a.length-i-1; j++){
                //这里-i主要是每遍历一次都把最大的i个数沉到最底下去了，没有必要再替换了
                if(a[j]>a[j+1]){
                    int temp = a[j];
                    a[j] = a[j+1];
                    a[j+1] = temp;
                }
            }
        }
        System.out.println();
        System.out.println("排序之后：");
        for (int i = 0; i < a.length; i++) {
            System.out.print(a[i]+" ");
        }
    }
}




//快排    不稳定
public class QuickSort {
    public static void main(String[] args) {
        int[] a={49,38,65,97,76,13,27,49,78,34,12,64,1,8};
        System.out.println("排序之前：");
        for (int i = 0; i < a.length; i++) {
            System.out.print(a[i]+" ");
        }
        //快速排序
        quick(a);
        System.out.println();
        System.out.println("排序之后：");
        for (int i = 0; i < a.length; i++) {
            System.out.print(a[i]+" ");
        }
    }

    private static void quick(int[] a) {
        if(a.length>0){
            quickSort(a,0,a.length-1);
        }
    }

    private static void quickSort(int[] a, int low, int high) {
        if(low<high){ //如果不加这个判断递归会无法退出导致堆栈溢出异常
            int middle = getMiddle(a,low,high);
            quickSort(a, 0, middle-1);
            quickSort(a, middle+1, high);
        }
    }

    private static int getMiddle(int[] a, int low, int high) {
        int temp = a[low];//基准元素
        while(low<high){
            //找到比基准元素小的元素位置
            while(low<high && a[high]>=temp){
                high--;
            }
            a[low] = a[high]; 
            while(low<high && a[low]<=temp){
                low++;
            }
            a[high] = a[low];
        }
        a[low] = temp;
        return low;
    }
}





//基数排序    稳定
import java.util.ArrayList;
import java.util.List;

public class RaSort {
    public static void main(String[] args) {
        int[] a={49,38,65,97,176,213,227,49,78,34,12,164,11,18,1};
        System.out.println("排序之前：");
        for (int i = 0; i < a.length; i++) {
            System.out.print(a[i]+" ");
        }
        //基数排序
        sort(a);
        System.out.println();
        System.out.println("排序之后：");
        for (int i = 0; i < a.length; i++) {
            System.out.print(a[i]+" ");
        }
    }

    @SuppressWarnings({ "rawtypes", "unchecked" })
	private static void sort(int[] array) {
        //找到最大数，确定要排序几趟
        int max = 0;
        for (int i = 0; i < array.length; i++) {
            if(max<array[i]){
                max = array[i];
            }
        }
        //判断位数
        int times = 0;
        while(max>0){
            max = max/10;
            times++;
        }
        //建立十个队列
        List<ArrayList> queue = new ArrayList<ArrayList>();
        for (int i = 0; i < 10; i++) {
            ArrayList queue1 = new ArrayList();
            queue.add(queue1);
        }
        //进行times次分配和收集
        for (int i = 0; i < times; i++) {
            //分配
            for (int j = 0; j < array.length; j++) {
                int x = array[j]%(int)Math.pow(10, i+1)/(int)Math.pow(10, i);
                ArrayList queue2 = queue.get(x);
                queue2.add(array[j]);
                queue.set(x,queue2);
            }
            //收集
            int count = 0;
            for (int j = 0; j < 10; j++) {
                while(queue.get(j).size()>0){
                    ArrayList<Integer> queue3 = queue.get(j);
                    array[count] = queue3.get(0);
                    queue3.remove(0);
                    count++;
                }
            }
        }
    }
}





//选择排序   不稳定
public class SelectSort {

    public static void main(String[] args) {
        int[] a={49,38,65,97,76,13,27,49,78,34,12,64,1,8};
        System.out.println("排序之前：");
        for (int i = 0; i < a.length; i++) {
            System.out.print(a[i]+" ");
        }
        //简单的选择排序
        for (int i = 0; i < a.length; i++) {
            int min = a[i];
            int n=i; //最小数的索引
            for(int j=i+1;j<a.length;j++){
                if(a[j]<min){  //找出最小的数
                    min = a[j];
                    n = j;
                }
            }
            a[n] = a[i];
            a[i] = min;
            
        }
        System.out.println();
        System.out.println("排序之后：");
        for (int i = 0; i < a.length; i++) {
            System.out.print(a[i]+" ");
        }
    }

}