【C++】Vector判断元素是否存在，去重，求交集，求并集

 1 #include <iostream>
 2 #include <vector>
 3 #include <algorithm> //sort函数、交并补函数
 4 #include <iterator> //求交并补使用到的迭代器
 5 using namespace std;
 6 
 7 //打印容器vector
 8 void print_vector(vector<int> v)
 9 {
10     if(v.size()>0)
11 {
12         cout<<"{";  
13         for(int i=0;i<int(v.size());i++)
14 {  
15             cout<<v[i]<<",";  
16         }  
17         cout<<"\b}";  
18     }
19     else{
20         cout<<"{}";
21     }
22 }
23 
24 //容器vector中元素的去重
25 vector<int> unique_element_in_vector(vector<int> v)
26 {
27     vector<int>::iterator vector_iterator;
28     sort(v.begin(),v.end());
29     vector_iterator = unique(v.begin(),v.end());
30     if(vector_iterator != v.end())
31 {
32         v.erase(vector_iterator,v.end());
33     }
34     return v;
35 }
36 
37 //两个vector求交集
38 vector<int> vectors_intersection(vector<int> v1,vector<int> v2)
39 {
40     vector<int> v;
41     sort(v1.begin(),v1.end());   
42     sort(v2.begin(),v2.end());   
43     set_intersection(v1.begin(),v1.end(),v2.begin(),v2.end(),back_inserter(v));//求交集 
44     return v;
45 }
46 
47 //两个vector求并集
48 vector<int> vectors_set_union(vector<int> v1,vector<int> v2)
49 {
50     vector<int> v;
51     sort(v1.begin(),v1.end());   
52     sort(v2.begin(),v2.end());   
53     set_union(v1.begin(),v1.end(),v2.begin(),v2.end(),back_inserter(v));//求交集 
54     return v;
55 }
56 
57 //判断vector的某一元素是否存在
58 bool is_element_in_vector(vector<int> v,int element)
59 {
60     vector<int>::iterator it;
61     it=find(v.begin(),v.end(),element);
62     if (it!=v.end())
63 {
64         return true;
65     }
66     else{
67         return false;
68     }
69 }
70 
71 int main()
72 {
73     vector<int> v1,v2,v;
74     v1.push_back(22);v1.push_back(22);v1.push_back(23);v2.push_back(23);v2.push_back(24);
75     cout<<"v1是否存在1这个元素？"<<is_element_in_vector(v1,1)<<endl;
76     cout<<"对v1去重：";
77     v1=unique_element_in_vector(v1);
78     print_vector(v1);
79     cout<<endl;
80     cout<<"求v1与v2的交集：";
81     v=vectors_intersection(v1,v2);
82     print_vector(v);
83     cout<<endl;
84     cout<<"求v1与v2的并集：";
85     v=vectors_set_union(v1,v2);
86     print_vector(v);
87     return 0;
88 }

转自：https://www.cnblogs.com/mayouyou/p/8921598.html 感谢博主！