STL库常用数据结构用法

介绍了map、vector、queue、set的使用。以及string与char【】的互相转换

#include <iostream>
#include <map>
#include <set>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>
#include <queue>
using namespace std;

void vectorTest() {
    struct {
        vector<int> m;
        int start, end, day;
    } teams[999];

    // add
    teams[0].m.insert(teams[0].m.begin() + 2, 2);
    teams[0].m.push_back(1);

    // del
    teams[0].m.clear();
    teams[0].m.erase(teams[0].m.begin() + 1, teams[0].m.end());

    teams[0].m.size();

    // query,update
    teams[0].m[0] = 0;
    int qwq = teams[0].m[0];

    //遍历
    for (auto it = teams[0].m.begin(); it != teams[0].m.end(); it++) {
        printf("%d\n", *it);
    }
    for (vector<int>::iterator it = teams[0].m.begin(); it != teams[0].m.end();
         it++) {
        printf("%d\n", *it);
    }
}

/*
    Map底层是红黑树，根据key排序
    unorderMap底层是哈希表，建议使用unorderMap。
*/
void mapTest() {
    unordered_map<string, int> strMap;

    // add
    char a[10] = "qwq";
    strMap.insert(make_pair("123", 2));
    strMap.insert(make_pair(a, 4));

    // update
    strMap[a] = 3;
    int test = strMap[a];

    // query
    for (auto it = strMap.begin(); it != strMap.end(); it++) {
        cout << it->first << " " << it->second << endl;
    }

    // del
    strMap.erase(strMap.find("123")); //根据key查找
    // strMap.clear();
}

/*
    底层实现是红黑树，mutiset元素可重复
*/
vector<int> testVector;
void setTest()
{
    testVector.push_back(1);//0
    testVector.push_back(5);//1
    testVector.push_back(2);//2
    testVector.push_back(3);//3
    testVector.push_back(4);//4
    //1,4,3,2,0
    struct cmp{
      bool operator()(const int &a,const int &b)
      {
          return testVector[a]>testVector[b];
      }  
    };
    set<int,cmp> s;

    //add
    s.insert(1);
    s.insert(0);
    s.insert(2);
    s.insert(3);
    s.insert(4);

    //query
    for(auto it=s.begin();it!=s.end();it++)
    {
        cout<<*it<<endl;
    }
    cout<<*s.find(123)<<endl;

    //del
    s.erase(s.find(0));

    //no update
}

/*
    优先队列，底层实现为堆，也可以用set实现。性能上在不同场景有较小差异。
*/
void queueTest()
{
    struct queueContent
    {   
        int num;
        queueContent(int num)
        {
            this->num = num;
        }
        bool operator<(const queueContent &a)const
        {
            return num<a.num; //堆顶为最大值
        }
    };
    priority_queue<queueContent> q;
    q.push(queueContent(1));
    q.push(queueContent(2));
    q.push(queueContent(3));

    while(!q.empty())
    {
        queueContent tmp = q.top();
        q.pop();
        cout<<tmp.num<<endl;
    }
    
}


void stringAndchar() {
    // String to char[]
    string pp = "dagah";
    char p[8];
    int i;
    for (i = 0; i < pp.length(); i++)
        p[i] = pp[i];
    p[i] = '\0';
    printf("%s\n", p);
    cout << p;

    //char[] to string
    char test[10]="qweqweasd";
    string test2 = test;
}


int main() { queueTest(); }