c++ STL container (2) set container

Set translates to a collection, which is the definition of a container set that is automatically ordered internally and does not contain repeated elements.

set<typename> name;

set<int> vi;
set<double> vi;
set<char> vi;
set<node> vi;//node可以是结构体

set<int> a[100]; //数组里面每个元素都是一个set集合

insert(x) insert x into the set container, and automatically increase sorting and de-duplication

	//insert(x) 将x插入set容器中,并自动递增排序和去重
	st.insert(4);
	st.insert(3);
	st.insert(1);
	st.insert(2);
	//不支持<it.end()的写法
	for(set<int>::iterator it=st.begin();it!=st.end();it++){
    
    
		cout<<*it<<" ";//1 2 3 4
	}

The traversal of the set collection
can only be traversed through iterators.
The stl containers other than vector and string do not support the *(it+i) access method.

//不支持<it.end()的写法
	for(set<int>::iterator it=st.begin();it!=st.end();it++){
    
    
		cout<<*it<<" ";//1 2 3 4
	}

The elements in the set are automatically sorted in ascending order, and duplicate elements are automatically removed

find(value) returns the iterator with the corresponding value in the set

set<int>::iterator it=st.find(3); //查找值为3的元素返回其迭代器 
	cout<<*it<<endl; //如果查找的元素不存在会返回最后一个元素的迭代器

erase() delete elements


//erase() 有两种用法一种是删除单个元素另一种是删除一个区间的所有元素
	//删除单个的方法又有两种
	//1.st.erase(it) it为所删元素的迭代器 可以和find连用 
	 //1 2 3 4
	st.erase(st.find(3)); 
	for(set<int>::iterator it=st.begin();it!=st.end();it++){
    
    
		cout<<*it<<" ";//1 2 4
	}
	cout<<endl;
	//2.st.erase(value) value为所删除元素的值 
	//1 2 4
	st.erase(1);
	for(set<int>::iterator it=st.begin();it!=st.end();it++){
    
    
		cout<<*it<<" ";//2 4
	}
	cout<<endl;
	st.insert(4);
	st.insert(3);
	st.insert(1);
	st.insert(2);
	//删除整个区间 
	//1 2 3 4
	st.erase(st.find(2),st.end());
	
	for(set<int>::iterator it=st.begin();it!=st.end();it++){
    
    
		cout<<*it<<" ";//1
	}

size() returns the number of elements in the set

  //1 2 3 4
    cout<<st.size(); //4

clear() clear all elements in st

	st.clear(); 
	cout<<st.size();

empty() Determine whether it is empty

	st.clear(); 
	cout<<st.empty()<<endl;//1 true

lower_bound(k)
upper_bound(k)

	st.insert(4);
	st.insert(3);
	st.insert(1);
	st.insert(2);
	//1 2 3 4
	//lower_bound(k) 返回一个迭代器，指向键值不小于k的第一个元素 
	set<int>::iterator it=st.lower_bound(2);//寻找第一个大于等于2的数 
	cout<<*it<<endl;//2
	//upper_bound(k) 返回一个迭代器，指向键值大于k的第一个元素 
	 it=st.upper_bound(2); 
	 cout<<*it<<endl;//3

c++ STL container (2) set container

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