java归并排序

import java.util.Arrays;

/**

* 归并排序

* 时间复杂度:O(nlogn)

* 稳定排序,耗内存

*/

public class MergeSort {

public static int[] sort(int[] nums) {

return sort(nums, 0, nums.length - 1);

}

private static int[] sort(int[] nums, int low, int high) {

int mid = (low + high) / 2;

if (low < high) {

// 左边

sort(nums, low, mid);

// 右边

sort(nums, mid + 1, high);

// 左右归并

merge(nums, low, mid, high);

}

return nums;

}

private 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;

// 把较小的数先移到新数组中

while (i <= mid && j <= high) {

if (nums[i] < nums[j]) {

temp[k++] = nums[i++];

} else {

temp[k++] = nums[j++];

}

}

// 把左边剩余的数移入数组

while (i <= mid) {

temp[k++] = nums[i++];

}

// 把右边边剩余的数移入数组

while (j <= high) {

temp[k++] = nums[j++];

}

// 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) {

int[] array = {2, 7, 8, 3, 1, 6, 9, 0, 5, 4};

System.out.println(Arrays.toString(MergeSort.sort(array)));

}

}