JAVA求字符串数组交集、并集和差集

1 package string;
2
3 import java.util.HashMap;
4 import java.util.HashSet;
5 import java.util.LinkedList;
6 import java.util.Map;
7 import java.util.Map.Entry;
8 import java.util.Set;
9
10 public class StringArray {
11     public static void main(String[] args) {
12         //测试union
13         String[] arr1 = {"abc", "df", "abc"};
14         String[] arr2 = {"abc", "cc", "df", "d", "abc"};
15         String[] result_union = union(arr1, arr2);
16         System.out.println("求并集的结果如下：");
17         for (String str : result_union) {
18             System.out.println(str);
19         }
20         System.out.println("---------------------可爱的分割线------------------------");
21
22         //测试insect
23         String[] result_insect = intersect(arr1, arr2);
24         System.out.println("求交集的结果如下：");
25         for (String str : result_insect) {
26             System.out.println(str);
27         }
28
29          System.out.println("---------------------疯狂的分割线------------------------");
30           //测试minus
31         String[] result_minus = minus(arr1, arr2);
32         System.out.println("求差集的结果如下：");
33         for (String str : result_minus) {
34             System.out.println(str);
35         }
36     }
37
38     //求两个字符串数组的并集，利用set的元素唯一性
39     public static String[] union(String[] arr1, String[] arr2) {
40         Set<String> set = new HashSet<String>();
41         for (String str : arr1) {
42             set.add(str);
43         }
44         for (String str : arr2) {
45             set.add(str);
46         }
47         String[] result = {};
48         return set.toArray(result);
49     }
50
51     //求两个数组的交集
52     public static String[] intersect(String[] arr1, String[] arr2) {
53         Map<String, Boolean> map = new HashMap<String, Boolean>();
54         LinkedList<String> list = new LinkedList<String>();
55         for (String str : arr1) {
56             if (!map.containsKey(str)) {
57                 map.put(str, Boolean.FALSE);
58             }
59         }
60         for (String str : arr2) {
61             if (map.containsKey(str)) {
62                 map.put(str, Boolean.TRUE);
63             }
64         }
65
66         for (Entry<String, Boolean> e : map.entrySet()) {
67             if (e.getValue().equals(Boolean.TRUE)) {
68                 list.add(e.getKey());
69             }
70         }
71
72         String[] result = {};
73         return list.toArray(result);
74     }
75
76     //求两个数组的差集
77     public static String[] minus(String[] arr1, String[] arr2) {
78         LinkedList<String> list = new LinkedList<String>();
79         LinkedList<String> history = new LinkedList<String>();
80         String[] longerArr = arr1;
81         String[] shorterArr = arr2;
82         //找出较长的数组来减较短的数组
83         if (arr1.length > arr2.length) {
84             longerArr = arr2;
85             shorterArr = arr1;
86         }
87         for (String str : longerArr) {
88             if (!list.contains(str)) {
89                 list.add(str);
90             }
91         }
92         for (String str : shorterArr) {
93             if (list.contains(str)) {
94                 history.add(str);
95                 list.remove(str);
96             } else {
97                 if (!history.contains(str)) {
98                     list.add(str);
99                 }
100             }
101         }
102
103         String[] result = {};
104         return list.toArray(result);
105     }
106 }