java第k个最小整数_输入n个整数，输出其中最小的k个

import java.util.Arrays;

import java.util.Scanner;

/*

* Declaration: All Rights Reserved !!!

*/

public class Main {

public static void main(String[] args) {

Scanner scanner = new Scanner(System.in);

// Scanner scanner = new Scanner(Main.class.getClassLoader().getResourceAsStream("data.txt"));

while (scanner.hasNext()) {

int n = scanner.nextInt();

int k = scanner.nextInt();

int[] arr = new int[n];

for (int i = 0; i < n; i++) {

arr[i] = scanner.nextInt();

}

// 【1】方法一

System.out.print(getMinK(arr, k));

// 【2】方法二

// Arrays.sort(arr);

// StringBuilder builder = new StringBuilder();

// for (int i = 0; i < k; i++) {

// builder.append(arr[i]).append(' ');

// }

//

// System.out.print(builder.substring(0, builder.length() - 1));

}

scanner.close();

}

private static String getMinK(int[] arr, int k) {

if (k <= 0) {

return "";

} else if (k >= arr.length) {

StringBuilder b = new StringBuilder();

for (int i : arr) {

b.append(i).append(' ');

}

return b.toString();

} else {

int[] min = new int[k];

for (int i = 0; i < arr.length; i++) {

if (i < k - 1) {

min[i] = arr[i];

} else if (i == k - 1) {

min[i] = arr[i];

// 下面要建大堆了

for (int j = min.length / 2; j >= 0; j--) {

shiftDown(min, j, min.length);

}

} else {

if (min[0] > arr[i]) {

min[0] = arr[i];

shiftDown(min, 0, min.length);

}

}

}

Arrays.sort(min);

StringBuilder b = new StringBuilder();

for (int i : min) {

b.append(i).append(' ');

}

return b.substring(0, b.length() - 1);

}

}

private static void shiftDown(int[] a, int i, int n) {

int child;

int tmp;

for (tmp = a[i]; 2 * i + 1 < n; i = child) {

// 左孩子

child = 2 * i + 1;

// 找较大的子结点

if (child + 1 < n && a[child] < a[child + 1]) {

child++;

}

if (tmp < a[child]) {

a[i] = a[child];

} else {

break;

}

}

a[i] = tmp;

}

}