排序算法的java实现

/**
 * 插入排序
 */
public class P4_3 {
    static void insertSort(int[] a){
        int j,t;
        /**
         *
         */
        for (int i = 0; i < a.length; i++) {
            t=a[i];
            j=i-1;
            while (j>=0&&t<a[j]){
                a[j+1]=a[j];
                j--;
            }
            a[j+1]=t;
        }

    }
    public static void main(String[] args){
        int[] a=new int[]{3,4,2,6,2,5,1,9,28};
        insertSort(a);
        for (int i = 0; i < a.length; i++) {
            System.out.println(a[i]);
        }

    }
}

/**
 * shell sort
 */
public class P4_4 {
    static void shellsort(int[] a){
        for (int r = a.length/2; r >=1 ; r/=2) {
            for (int i = r; i < a.length; i++) {
                int t=a[i];
                int j=i-r;
                while (j>=0&&t<a[j]){
                    a[j+r]=a[j];
                    j=j-r;
                }
                a[j+r]=t;
            }
        }
    }
    public static void main(String[] args){
        int[] a=new int[]{3,4,2,6,25,1,9,28};
        shellsort(a);
        for (int i = 0; i < a.length; i++) {
            System.out.println(a[i]);
        }
    }
}

/**
 * qicksort
 */
public class P4_5 {
    static void qicksort(int[] a,int left,int right){
        int f,t;
        int rtemp,ltemp;
        rtemp=right;
        ltemp=left;
        f=a[(right+left)/2];
        while (ltemp<rtemp){
            while (a[ltemp]<f){
                ltemp++;
            }
            while (a[rtemp]>f){
                rtemp--;
            }
            if (ltemp<rtemp){
                //将左边大于分界值得数交换到邮编小于分界值得位置
                t=a[rtemp];
                a[rtemp]=a[ltemp];
                a[ltemp]=t;
                ltemp++;
                rtemp--;
            }
        }
        if (ltemp==rtemp){
            ltemp++;
        }
        if (right>ltemp){
            qicksort(a,rtemp+1,right);
        }
        if (rtemp>left){
            qicksort(a,left,ltemp-1);
        }
    }
    public static void main(String[] args){
        int[] a=new int[]{3,4,2,6,25,1,9,73};
        qicksort(a,0,a.length-1);
        for (int i = 0; i < a.length; i++) {
            System.out.println(a[i]);
        }

    }
}

/**
 * heapsort
 */
public class P4_6 {
    static void heapsort(int[] a,int n){
        int i,j,h,k;
        int t;
        //构建堆
        for (i = n/2-1; i >=0 ; i--) {//找到当前最后一个节点的父节点
            //存在右子树
            while (2*i+1<n){
                j=2*i+1;
                if (j+1<n){
                    if (a[j]<a[j+1]){
                        j++;
                    }
                }
                //将最大的放在节点位置
                if (a[i]<a[j]){
                    t=a[i];
                    a[i]=a[j];
                    a[j]=t;
                    i=j;
                }else {
                    break;
                }
            }
        }
        //输出堆：
        System.out.println("输出的堆：");
        for (int l = 0; l < a.length; l++) {
            System.out.print(a[l]);
            System.out.print(" ");
            System.out.println();
        }

        //找出最大
        for (i = n-1; i >=0 ; i--) {
            //将找到的数据放在最右边
            t=a[0];
            a[0]=a[i];
            a[i]=t;
            k=0;
            //k存在有子树
            while ((2*k+1)<i){
                j=2*k+1;
                if((j+1)<i){
                    if (a[j]<a[j+1]){
                        j++;
                    }
                }
                if (a[k]<a[j]){
                    t=a[k];
                    a[k]=a[j];
                    a[j]=t;
                    k=j;
                }else {
                    break;
                }
            }


        }

    }
    public static void main(String[] args){
        int[] a=new int[]{1,3,5,7,9,2,4,6,8,0};
        heapsort(a,a.length);
        for (int l = 0; l < a.length; l++) {
            System.out.print(a[l]);
            System.out.print(" ");
        }
    }
}

/**
 * mergesort
 */
public class P4_7 {
    static void mergeone(int[] a,int[] b,int n,int len){
        int i,j,k,s,e;
        s=0;//开始位置
        while ((s+len)<n){
            //结束位置
            e=s+2*len-1;
            if (e>n){
                e=n-1;
            }
            //合并
            k=s;
            i=s;
            j=s+len;
            while (i<(s+len)&&j<=e){
                if (a[i]<a[j]){
                    b[k++]=a[i++];
                }else {
                    b[k++]=a[j++];
                }
            }
            //将未合并的数组复制
            while (i<(s+len)){
                b[k++]=a[i++];
            }
            while (j<=e){
                b[k++]=a[j++];
            }
            s=e+1;//下一次开始的位置

        }
        //没有比较的合并过来
        if (s<n){
            for (;s<n;s++){
                b[s]=a[s];
            }
        }
    }
    static void mergesort(int[] a,int n){
        int[] p=new int[n];
        int f,len;
        len=1;
        f=0;
        while (len<n){
            if (f==1){
                mergeone(p,a,n,len);
            }else {
                mergeone(a,p,n,len);
            }
            len=2*len;
            f=1-f;
        }
        if (f==1){
            for (int h = 0; h < n; h++) {
                a[h]=p[h];
            }
        }
    }
    public static void main(String[] args){
        int[] a=new int[]{3,4,2,6,25,1,9,92,19};
        mergesort(a,a.length);
        for (int i = 0; i < a.length; i++) {
            System.out.println(a[i]);
        }
    }
}