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test29.java
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54 lines (49 loc) · 1.35 KB
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package byteDance;
/**
* Created by lizeyang on 2020/5/15.
* 归并排序,so easy~
*/
public class test29 {
//时间复杂度O(nlogn)，稳定
public static int[] sort(int[] nums) {
if (nums == null || nums.length == 0) {
return nums;
}
mergeSort(nums, 0, nums.length - 1);
return nums;
}
public static void mergeSort(int[] nums, int l, int r) {
if (l >= r) {
return;
}
int mid = (l + r) >> 1;
mergeSort(nums, l, mid);
mergeSort(nums, mid + 1, r);
partition(nums, l, mid, r);
}
public static void partition(int[] nums, int l, int mid, int r) {
int[] help = new int[r - l + 1];
int p = l;
int q = mid + 1;
int index = 0;
while (p <= mid && q <= r) {
help[index++] = nums[p] < nums[q] ? nums[p++] : nums[q++];
}
while (p <= mid) {
help[index++] = nums[p++];
}
while (q <= r) {
help[index++] = nums[q++];
}
for (int i = 0; i < help.length; i++) {
nums[l + i] = help[i++];
}
}
public static void main(String[] args) {
int[] nums = {1, 3, 4, 6, 2, 8, 5};
int[] res = sort(nums);
for (int i = 0; i < res.length; i++) {
System.out.print(res[i] + " ");
}
}
}