📅  最后修改于: 2022-03-11 14:52:23.186000             🧑  作者: Mango
// Java code for kth smallest element in an array
import java.util.Arrays;
import java.util.Collections;
class GFG {
// Standard partition process of QuickSort.
// It considers the last element as pivot
// and moves all smaller element to left of
// it and greater elements to right
public static int partition(Integer[] arr, int l,
int r)
{
int x = arr[r], i = l;
for (int j = l; j <= r - 1; j++) {
if (arr[j] <= x) {
// Swapping arr[i] and arr[j]
int temp = arr[i];
arr[i] = arr[j];
arr[j] = temp;
i++;
}
}
// Swapping arr[i] and arr[r]
int temp = arr[i];
arr[i] = arr[r];
arr[r] = temp;
return i;
}
// This function returns k'th smallest element
// in arr[l..r] using QuickSort based method.
// ASSUMPTION: ALL ELEMENTS IN ARR[] ARE DISTINCT
public static int kthSmallest(Integer[] arr, int l,
int r, int k)
{
// If k is smaller than number of elements
// in array
if (k > 0 && k <= r - l + 1) {
// Partition the array around last
// element and get position of pivot
// element in sorted array
int pos = partition(arr, l, r);
// If position is same as k
if (pos - l == k - 1)
return arr[pos];
// If position is more, recur for
// left subarray
if (pos - l > k - 1)
return kthSmallest(arr, l, pos - 1, k);
// Else recur for right subarray
return kthSmallest(arr, pos + 1, r, k - pos + l - 1);
}
// If k is more than number of elements
// in array
return Integer.MAX_VALUE;
}
// Driver program to test above methods
public static void main(String[] args)
{
Integer arr[] = new Integer[] { 12, 3, 5, 7, 4, 19, 26 };
int k = 3;
System.out.print("K'th smallest element is " + kthSmallest(arr, 0, arr.length - 1, k));
}
}
// This code is contributed by Chhavi