import java.lang.reflect.Array;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
public class Test {
public static int[] sort(int[] nums, int low, int high) {
//System.out.println(Arrays.toString(nums));
int mid = (low + high) / 2;
System.out.println(low + " " + mid + " " + high);
if (low < high) {
// 左边
sort(nums, low, mid);
// 右边
sort(nums, mid + 1, high);
// 左右归并
System.out.println("beg merge --- " + low + " " + mid + " " + high);
merge(nums, low, mid, high);
System.out.println(Arrays.toString(nums));
}
return nums;
}
public static void merge(int[] nums, int low, int mid, int high) {
int[] temp = new int[high - low + 1];
int i = low; // 左指针
int j = mid + 1; // 右指针
int k = 0; // 临时数组指针
// 把较小的数先移到新数组中
// mid作为分界点比较
while (i <= mid && j <= high) {
if (nums[i] < nums[j]) {
temp[k++] = nums[i++];
} else {
temp[k++] = nums[j++];
}
}
System.out.println("1" + Arrays.toString(temp));
// 把左边剩余的数移入数组
while (i <= mid) {
temp[k++] = nums[i++];
}
System.out.println("2 " + Arrays.toString(temp));
// 把右边边剩余的数移入数组
while (j <= high) {
temp[k++] = nums[j++];
}
System.out.println("3 " + Arrays.toString(temp));
// 把新数组中的数覆盖nums数组
for (int k2 = 0; k2 < temp.length; k2++) {
nums[k2 + low] = temp[k2];
}
}
public static void main(String[] args) {
// TODO Auto-generated method stub
int[] nums = {5, 4, 3, 2, 1};// 6, 9, 0, 5, 4 };
System.out.println(Arrays.toString(nums));
sort(nums, 0, nums.length - 1);
System.out.println(Arrays.toString(nums));
Integer[] a = new Integer[] { 3, 2, 32, 3 };
List<Integer> list = (List<Integer>) Arrays.asList(a);
Collections.sort(list);
for (int i = 0; i < list.size(); i++) {
System.out.println(list.get(i));
}
System.out.println("test");
}
}
Collections.sort(list); 里使用的归并排序
其实就是对数组递归拆分两个数组,或者更多,然后几个数组进行归并,然后依次添加到临时数组中, 临时数组最后也是有序的,然后再用临时数组来修改原数组.