c_cpp 设置语法

Posted 2021-05-14

#include <bits/stdc++.h>
using namespace std;

// #CPP_STL #Sets #BasicProblem
// https://www.geeksforgeeks.org/set-in-cpp-stl/



int main() {
    // A set stores elements in sorted order
    // Does NOT contain duplicates
    set<int> s;
    
    // =====(IMP)==========
    // use unordered_set if sorted order is not required
    s.insert(25);
    s.insert(25); // Only one 25 will be added to set
    s.insert(28);
    s.insert(22);
    s.insert(2);
    for(auto it=s.begin();it!=s.end();it++){
        cout<<*it<<" "; // *it = value at it
    }
    cout<<endl;
    
//================( find(element) )===========================
    // s.find returns iterator if found, else returns s.end()
    auto it=s.find(28);
    if(it!=s.end()){
        cout<<"28 is found"<<endl;
    }

//=================(find if an element is present)==================
// =================(s.count(element)==========================
    if (hashset.count(2) <= 0) {
        cout << "Key 2 is not in the hash set." << endl;
    }

//=================( erase(iterator) )=============================
    if(s.find(28)!=s.end()){ // check if element is present before trying to delete
        s.erase(s.find(28));  // trying to delete a non-existent element returns error 
    }
    
    for(auto it=s.begin();it!=s.end();it++){
        cout<<*it<<" "; // *it = value at it
    }
    cout<<endl;
    it=s.find(28);
    if(it!=s.end()){
        cout<<"28 is found"<<endl;
    }else{
        cout<<"28 is not found"<<endl;
    }
    
    it=s.find(38);
    if(it!=s.end()){
        cout<<"38 is found"<<endl;
    }else{
        cout<<"38 is not found"<<endl;
    }
    
	return 0;
}