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test41.java
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52 lines (48 loc) · 1.35 KB
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package byteDance;
/**
* Created by lizeyang on 2020/5/16.
* 数组中第k大的数
*/
public class test41 {
//利用快排或者归并排序，再取值即可
public static int sort(int[] nums, int k) {
if (nums == null || nums.length == 0) {
return 0;
}
mergeSort(nums, 0, nums.length - 1);
if (k > nums.length || k < 0) {
return 0;
}
return nums[k - 1];
}
public static void mergeSort(int[] nums, int l, int r) {
if (l < r) {
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 p = l;
int q = mid + 1;
int[] help = new int[r - l + 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, 4, 6, 2, 8, 4};
System.out.println(sort(nums, 5));
}
}