归并排序
import java.text.SimpleDateFormat;
import java.util.Arrays;
import java.util.Date;
public class MergetSort {
public static void main(String[] args) {
int[] arr = new int[80000000];
for (int i = 0; i < 80000000; i++) {
arr[i] = (int) (Math.random() * 8000000);
}
System.out.println("排序前");
Date data1 = new Date();
SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String date1Str = simpleDateFormat.format(data1);
System.out.println("排序前的时间是=" + date1Str);
int temp[] = new int[arr.length];
mergeSort(arr, 0, arr.length - 1, temp);
Date data2 = new Date();
String date2Str = simpleDateFormat.format(data2);
System.out.println("排序前的时间是=" + date2Str);
}
public static void mergeSort(int[] arr, int left, int right, int[] temp) {
if(left < right) {
int mid = (left + right) / 2;
mergeSort(arr, left, mid, temp);
mergeSort(arr, mid + 1, right, temp);
merge(arr, left, mid, right, temp);
}
}
public static void merge(int[] arr, int left, int mid, int right, int[] temp) {
int i = left;
int j = mid + 1;
int t = 0;
while (i <= mid && j <= right) {
if(arr[i] <= arr[j]) {
temp[t] = arr[i];
t += 1;
i += 1;
} else {
temp[t] = arr[j];
t += 1;
j += 1;
}
}
while( i <= mid) {
temp[t] = arr[i];
t += 1;
i += 1;
}
while( j <= right) {
temp[t] = arr[j];
t += 1;
j += 1;
}
t = 0;
int tempLeft = left;
while(tempLeft <= right) {
arr[tempLeft] = temp[t];
t += 1;
tempLeft += 1;
}
}
}