1 import java.util.HashMap;
2 import java.util.Iterator;
3 import java.util.Map;
4
5 public class Demo5 {
6
7 public static void main(String[] args) {
8
9 int[] arr = new int[]{3, 4, 5, 9, 8};
10 int num = 8;
11 int[] ret = getIndex(arr, num);
12 System.out.println("index of two number:" + ret[0]+" " + ret[1]);
13
14 }
15
16 //找到这两个数的下标，并以长度为2的数组形式返回
17 public static int[] getIndex(int[] arr, int num){
18
19 int[] ret = new int[2]; //长度为2的数组
20 HashMap<Integer, Integer> hashMap = new HashMap<>();
21 int index = 0;
22
23 //将每个数字及其下标放入map中
24 for (int i : arr) {
25 hashMap.put(i, index++ );
26 }
27
28 //遍历 HashMap 并判断
29 Iterator iterator = hashMap.entrySet().iterator();
30 while (iterator.hasNext()){
31 Map.Entry entry = (Map.Entry)iterator.next();
32
33 int value = (int) entry.getKey();
34 int subValue = num - value;
35
36 if (hashMap.containsKey(subValue)){
37 //找到了
38 ret[0] = (int) entry.getValue();
39 ret[1] = hashMap.get(subValue);
40 break;
41 }
42 }
43 return ret;
44
45 }
46 }
