Dynamic array vector
Note:
1: Before finding the union and intersection, you need to sort the two arrays (both int or vector), otherwise the result will be wrong.
2: The size of the vector needs to be defined , otherwise the result may not be obtained
Union set_union( ) :
int main()
{
int a[4]={
1,2,3,4}; //已经有序，若无序，需要排序！
int b[4]={
2,3,4,5};
vector<int> c(8); //需要定义大小
set_union(a,a+4,b,b+4,c.begin()); //并集
for(auto x:c){
cout<<x<<" ";
}
return 0;
}
operation result:
Intersection set_intersection( ) :
int main()
{
int a[4]={
1,2,3,4}; //已经有序，若无序，需要排序！
int b[4]={
2,3,4,5};
vector<int> c(8); //需要定义大小
set_intersection(a,a+4,b,b+4,c.begin()); //交集
for(auto x:c){
cout<<x<<" ";
}
return 0;
}
operation result:
If you don't want the following 0 to appear, take the intersection as an example:
int main()
{
int a[4]={
1,2,3,4}; //已经有序，若无序，需要排序！
int b[4]={
2,3,4,5};
vector<int> c(8);
vector<int>::iterator it=set_intersection(a,a+4,b,b+4,c.begin()); //交集 返回位置到it
cout<<it-c.begin()<<endl; //交集中元素个数
for(int i=0;i<it-c.begin();i++) //输出这些元素
cout<<c[i]<<" ";
return 0;
}
operation result:
Set
The difference between a set and a vector is:
1: No sorting, because the set itself is ordered and non-repetitive
2: The fifth parameter of set_union and set_intersection isinserter(c，c.begin() )
Union set_union( ) :
int main()
{
set<int> a,b,c;
for(int i=1;i<5;i++) //a: 1 2 3 4
a.insert(i);
for(int i=2;i<6;i++) //b: 2 3 4 5
b.insert(i);
set_union(a.begin(),a.end(),b.begin(),b.end(),inserter(c,c.begin())); //并集
for(auto x:c){
cout<<x<<" ";
}
return 0;
}
operation result:
Intersection set_intersection( ) :
int main()
{
set<int> a,b,c;
for(int i=1;i<5;i++) //a: 1 2 3 4
a.insert(i);
for(int i=2;i<6;i++) //b: 2 3 4 5
b.insert(i);
set_intersection(a.begin(),a.end(),b.begin(),b.end(),inserter(c,c.begin())); //交集
for(auto x:c){
cout<<x<<" ";
}
return 0;
}
operation result:
