Detailed set of common usage

set as a collection of translation, it is a internal self-ordering and no repeating elements of the container

head File

#include<set>
using namespace std;

Defined set of

Single set

set<typename> name;

set<int> name;
set<double> name;
set<char> name;
set<node> name;	// node是结构体的类型

set array

set<typename> ArrayName[arraySize];
set<int> a[1000];

Set inside a container element access

Can only be accessed by the iterator

set<typename>::iterator it;

In addition to vector and string of STL containers can not be used * (it + i) access methods , we can only enumerate:

#include<cstdio>
#include<set>
using namespace std;

int main(){
    set<int> st;
    st.insert(3);
    st.insert(5);
    st.insert(2);
    st.insert(3);

    // 注意：不支持it < st.end()写法
    for(set<int>::iterator it = st.begin(); it != st.end(); it++){
        printf("%d ", *it);
    }

    return 0;
}

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The results can be found by the elements in the set automatically in ascending order, and automatically removing repetitive elements

set of commonly used functions

insert( )

insert(x)X set may be inserted into the container, and automatically in ascending order and de-emphasis, time complexity is O(logN) , N is the number of elements in the set

find( )

find(value) Returns the value of the corresponding set value of the iterator, time complexity is O(logN) , N is the number of elements in the set

#include<cstdio>
#include<set>
using namespace std;

int main(){
    set<int> st;
    for(int i = 1; i <=10; i += 2){
        st.insert(i);
    }

    for(set<int>::iterator it = st.begin(); it != st.end(); it++){
        printf("%d ", *it);
    }

    set<int>::iterator it = st.find(7);

    printf("\n%d\n", *it);

    return 0;
}

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7

erase( )

Delete individual items

st.erase(it), It is required to remove elements of the iterator, time complexity O(1), it can be combined find()using

#include<cstdio>
#include<set>
using namespace std;

int main(){
    set<int> st;
    st.insert(100);
    st.insert(200);
    st.insert(100);
    st.insert(300); 
    st.erase(st.find(100)); // 利用find找到100，然后用erase删除
    st.erase(st.find(200));
    for(set<int>::iterator it = st.begin(); it != st.end(); it++)
        printf("%d", *it);
    return 0;
}

st.erase(value), valueTo remove the element of a desired value, the time complexity O(logN), Nas setthe number of elements

#include<cstdio>
#include<set>
using namespace std;

int main(){
    set<int> st;
    st.insert(100);
    st.insert(200);
    st.insert(100);
    st.insert(300);
    st.erase(100); // 删除set中值为100的元素

    for(set<int>::iterator it = st.begin(); it != st.end(); it++)
        printf("%d ", *it);
    return 0;
}

Delete elements within a range

st.erase(first, last)You can delete all the elements within a range, delete interval is the [first, last)time complexity isO(last - first)

#include<cstdio>
#include<set>
using namespace std;

int main(){
    set<int> st;
    st.insert(100);
    st.insert(200);
    st.insert(100);
    st.insert(300);

    set<int>::iterator it = st.find(200);
    st.erase(it, st.end()); // 删除元素200至set末尾之间的元素，即200,300

    for(set<int>::iterator it = st.begin(); it != st.end(); it++)
        printf("%d ", *it);
    return 0;
}

size( )

size()Used to obtain the number of elements within the set, the time complexity isO(1)

#include<cstdio>
#include<set>
using namespace std;

int main(){
    set<int> st;
    st.insert(100);
    st.insert(200);
    st.insert(100);
    st.insert(300);

    printf("%d", st.size());
    return 0;
}

clear( )

clear()To clear all of the elements in the set, the complexity ofO(N)

#include<cstdio>
#include<set>
using namespace std;

int main(){
    set<int> st;
    st.insert(100);
    st.insert(200);
    st.insert(100);
    st.insert(300);
    st.clear();
    printf("%d", st.size());
    return 0;
}

Common uses set of

To automatically re-sorted in ascending

Write by Gqq

Algorithms notes - Standard Template Library STL - set