STL常用库函数复习

常用库函数复习"/>

STL常用库函数复习

文章目录

• pair
• vector
• list
• stack
• queue
• • queue
  • priority_queue
  • queue双端队列
• set
• • ✨set集合
  • ✨multiset 多重集合
  • 了解：unordered_set 无序集合
• map
• • 🌟map
  • 几乎不用：multimap
  • 一般不用：undered_map

pair

• utility
• 示例

#include <iostream>
#include <utility>using namespace std;int main() {pair<int,double> p1(1,3.14);pair<char,string> p2('a',"hello");cout<<p1.first<<", "<<p1.second<<endl;cout<<p2.first<<", "<<p2.second<<endl;return 0;
}

• 嵌套
• 例如：三维坐标

#include <iostream>
#include <utility>using namespace std;int main() {pair<int,int> p1(1,2);pair<int,pair<int,int>> p2(3,make_pair(4, 5));pair<pair<int,int>,pair<int,int>> p3(make_pair(6, 7),make_pair(3, 5));cout<<p1.first<<", "<<p1.second<<endl;cout<<p2.first<<", "<<p2.second.first<<", "<<p2.second.second<< endl;cout<<p3.first.first<<" ,"<<p3.first.second<<" ,"<<p3.second.first<<" ,"<<p3.second.second<<endl;return 0;
}

• 示例

#include <iostream>
#include <utility>
#include <vector>using namespace std;
struct Person{string name;int age;
};
int main() {vector<Person> people;people.push_back({"Alice",25});people.push_back({"Bob",30});people.push_back({"Charlie",20});vector<pair<Person, int>> scores;scores.push_back({people[0],90});scores.push_back({people[1],85});scores.push_back({people[2],95});for(const auto& pair : scores){cout<<"Name: "<<pair.first.name<<endl;cout<<"Age: "<<pair.first.age<<endl;cout<<"Score: "<<pair.second<<endl;cout<<endl;}return 0;
}

vector

• 一般用 i<size()或者 (int)size()，如果vector 为空，size()-1 会是很大的数

• push_back()

• pop_back()

• insert()

• erase()

• empty()

• resize()

• begin(),end()

• clear()

• sort()

• unique()

• 排序并去重：vec.erase(unique(vec.begin(),vec.end()),vec.end());

#include <iostream>
#include <vector>
#include <algorithm>int main() {std::vector<int> vec = {2,1,3,2,4,1,5,4};std::sort(vec.begin(),vec.end());auto last = unique(vec.begin(),vec.end());vec.erase(last,vec.end());for(const auto& num:vec){std::cout<<num<<" ";}return 0;
}

list

• 用的很少，如果需要链表一般用数组模拟或手写链表
• 如果需要随机访问，一半用 vector(),deque()
• push_back()
• push_front()
• pop_back()
• pop_front()
• size()
• empty()
• clear()
• front()
• back()
• begin()
• end()
• insert()
• erase()

stack

• push()
• pop()
• top()
• empty()
• size()
• 将数组元素依次入栈，再依次出栈，可以将数组翻转。（一般不会这么做）

queue

queue

以下都是 O(1)

• push(x)
• pop()
• front()
• empty()
• size()

priority_queue

• push(x)

• pop()

• top()

• empty()

• size()

• #include

• priority_queue(int，vector,compare/greater) //小根堆

struct Compare{bool operator()(int a,int b){return a>b;}
}

queue双端队列

• 不常用
• push_back(x)
• push_front(x)
• pop_back()
• pop_front()
• front()
• back()
• empty()
• size()
• clear()
  

#include<bits/stdc++.h>using namespace std;int main(){ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);int m;cin>>m;queue<string> V,N;while(m--){string op;cin>>op;if(op=="IN"){string name,q;cin>>name>>q;if(q=="V")V.push(name);else N.push(name);}else{string q;cin>>q;if(q=="V")V.pop();else N.pop();}}while (V.size()) {cout<<V.front()<<'\n';V.pop();}while(N.size()){cout<<N.front()<<"\n";N.pop();}return 0;
}

#include<bits/stdc++.h>using namespace std;
using ll = long long;int main(){ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);int n;cin>>n;priority_queue<ll,vector<ll>,greater<ll>> pq;for(int i=1;i<=n;++i){ll x;cin>>x;pq.push(x);}ll ans = 0;while(pq.size()>=2){ll x = pq.top();pq.pop();ll y = pq.top();pq.pop();ans += x+y;pq.push(x+y);}cout<<ans<<"\n";return 0;
}

set

✨set集合

• 无重复，默认降序
• insert(x)
• erase(x)
• find(x)

#include<iostream>
#include<set>
using namespace std;
int main( ){set<int,greater<int>> mySet;mySet.insert(25);mySet.insert(17);mySet.insert(39);mySet.insert(42);for(const auto& elem:mySet)cout<<elem<<" ";cout<<endl;return 0;
}

#include<iostream>
#include<set>
using namespace std;struct MyCompare{bool operator()(const int& a,const int& b)const{return a>b;}
};int main( ){set<int,MyCompare> mySet;mySet.insert(25);mySet.insert(17);mySet.insert(39);mySet.insert(42);for(const auto& elem : mySet){cout<< elem << " ";}cout<<endl;return 0;
}

✨multiset 多重集合

• 允许存储重复元素
• 二分：
  • lower_bound:返回第一个不小于给定值的迭代器
  • upper_bount:返回第一个不大于给定值的迭代器
• st.erase(st.find(x))

了解：unordered_set 无序集合

• 无重复，无顺序

map

🌟map

• 存储键值对

#include <iostream>  
#include <map>  
using namespace std;  int main() {  //创建并初始化multimap  multimap<int, string> myMultimap = {{1, "Apple"}, {2, "Banana"}, {3, "Orange"}};  //判断元素是否存在  if (myMultimap.count(2) == 0) {  cout << "Key 2 not found." << endl;  }  //插入元素  myMultimap.insert(make_pair(4, "Grapes"));  //清空multimap  myMultimap.clear();  //判断multimap是否为空  if (myMultimap.empty()) {  cout << "Multimap is empty." << endl;  } else {  //查找和访问元素  auto range = myMultimap.equal_range(3);  for (auto it = range.first; it != range.second; ++it) {  cout << "Key: " << it->first << ", Value: " << it->second << endl;  }  }  //遍历并打印multimap中的元素  for (const auto& pair : myMultimap) {  cout << "Key: " << pair.first << ", Value: " << pair.second << endl;  }  //删除元素  myMultimap.erase(3);  return 0;  
}

几乎不用：multimap

一般不用：undered_map