现有1~100共一百个自然数，已随机放入一个有98个元素的数组a[98]。

Question

要用JAVA实现
要求写出一个尽量简单的方案，找出没有被放入数组的那2个数，并在屏幕上打印这2个数。注意：程序不用实现自然数随机放入数组的过程。

Answer 1

有人给出了一个时间复杂度O(n^2)的算法，我给一个O(n)的算法把：public void printNum(int[] arr) {&nbsp; &nbsp; int[] result = new int[2];&nbsp; &nbsp; int[] heap = new int[101];&nbsp; &nbsp; for (int i = 0; i < 98; i++) {&nbsp; &nbsp; &nbsp; &nbsp; heap[arr[i]] = 1;&nbsp; &nbsp; }&nbsp; &nbsp; for (int i = 1; i <= 100; i++) {&nbsp; &nbsp; &nbsp; &nbsp; if (heap[i] != 1) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; System.out.println(i);&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; }}

Answer 2

public int[] findNum(int[] arr) {&nbsp; &nbsp; int[] result = new int[2];&nbsp; &nbsp; var count = 0;&nbsp; &nbsp; for (int i = 1; i <= 100; i++) {&nbsp; &nbsp; &nbsp; if (count == 2) break;&nbsp; &nbsp; &nbsp; if (arr.indexOf(i) == -1) {&nbsp; &nbsp; &nbsp; &nbsp; result.push(i);&nbsp; &nbsp; &nbsp; &nbsp; count++;&nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; }&nbsp; &nbsp; return result;}