合并排序
public class MergeSort{
public static void merge(int[]c,int[]d,int l,int m,int r){
//合并c[l:m]和c[m+1:r]到d[l:r]
int i=l,j=m+1,k=l;
while((i<=m)&&(j<=r))//保证数组中还有元素
if(c[i]<=c[j])
d[k++]=c[i++];
else d[k++]=c[j++];//谁小把谁放入数组d中,写完之后再执行“++”操作
if(i>m)//j还有剩余,剩余元素直接写下来
for(int q=j;q<=r;q++)
d[k++]=c[q];
else//i还有剩余,剩余元素直接写下来
for(int q=i;q<=m;q++)
d[k++]=c[q];
}
public static void mergePass(int []x,int []y,int s){
//合并大小为s的相邻子数组
int i=0;
while (i<=x.length-2*s)
{
//合并大小为s的相邻2段子数组
merge(x,y,i,i+s-1,i+2*s-1);
i=i+2*s;
}
//剩下的元素个数少于2s
if (i+s<x.length)
merge(x,y,i,i+s-1,x.length-1);
else
//复制到y
for (int j=i;j<x.length;j++)
y[j]=x[j];
}
public static void mergeSort(int a[])
{
int[]b=new int[a.length];
int s=1;
while(s<a.length){
mergePass(a,b,s);//将a中数经规模s合并到数组b中
s=s+s;
mergePass(b,a,s);//将合并到b中数经规模s合并到数组a中
s=s+s;
}
}
public static void main (String[] args){
int[] a={6,8,12,71,36,28,46,72,10,9};
mergeSort(a);
for(int i=0;i<a.length;i++)
System.out.print(a[i]+" ");
}
}
快速排序
public class QuickSort {
private static int Partition(int[] arr, int start, int end) {
//arr[start]为挖的第一个坑
int key = arr[start];
while (start < end) {
while (arr[end] >= key && end > start)
end--;
arr[start] = arr[end];
while (arr[start] <= key && end > start)
start++;
arr[end] = arr[start];
}
arr[start] = key;
return start;
}
public static void quickSort(int[] arr, int start, int end) {
if (start < end) {
int index = Partition(arr, start, end);
quickSort(arr, start, index - 1);
quickSort(arr, index + 1, end);
}
}
public static void main (String[] args){
int[] a={6,8,12,71,36,28,46,72,10,9};
quickSort(a,0,9);
for(int i=0;i<a.length;i++)
System.out.print(a[i]+" ");
}
}