目录：
- set初始化、遍历、查找、插入、下标
1.1 set的初始化
1.2 set的遍历
1.3 set的查找
1.4 set的插入
1.5 set的下标访问
1.6 set的修改- map初始化、遍历、查找、插入、下标
2.1 map的初始化
2.2 map的遍历
2.3 map的查找
2.4 map的插入
2.5 map的下标访问
1. set初始化、遍历、查找、插入、下标
set的特点：
1、关键字必须唯一，不能重复
2、默认情况下，set中的key会按照升序进行排序
3、set的底层实现是红黑树
1.1 set的初始化
set number = {1, 3, 5, 8, 9, 3, 4, 3, 5};//1、使用大括号初始化
或
int arr[10] = {1, 8, 9, 5, 3, 7, 2, 3};
set number(arr, arr + 10);//2、使用迭代器范围的形式
1.2 set的遍历
迭代器可以看成是一个高级指针
set::iterator it;//声明迭代器
for(it = number.begin(); it != number.end(); ++it)
{
cout << it << " ";
}
cout << endl;
或
/ auto a = 10; */ //当有错误时加上这条
for(auto &elem : number)
{
cout << elem << " ";
}
cout << endl;
1.3 set的查找
size_t cnt1 = number.count(9);
size_t cnt2 = number.count(10);
cout << "cnt1 = " << cnt1 << endl;
cout << "cnt2 = " << cnt2 << endl;
或
/* auto it2 = number.find(10); */
auto it2 = number.find(9); //在set中找值为9的数
if(it2 == number.end()) //若找到默认都没找到
{
cout << “该元素不存在set中” << endl;
}
else //若找到了
{
cout << *it2 << endl;
}
cout << endl;
1.4 set的插入
pair<set::iterator, bool> ret = number.insert(7); //插入7
if(ret.second) //上面ret的那一行的bool也就是ret.second
{
cout << “插入成功” << endl;
}
else
{
cout << “插入失败” << endl;
}
//遍历
for(auto &elem : number)
{
cout << elem << " ";
}
cout << endl;
1.5 set的下标访问
下标访问,set不支持下标访问
cout << endl;
/* cout << number[0] << endl;//error */
1.6 set的修改
set不能进行修改，为了保证红黑树结构的稳定
cout <<endl << “修改” << endl;
it = number.begin();
cout << it << endl;
/ *it = 100;//error */
2. map初始化、遍历、查找、插入、下标
map特点：
map特点
1、key值必须唯一，不存在相同的key，但是value值可以相同，也可以不同
2、默认情况下，按照key值进行升序排列
3、set的底层实现是红黑树
（尝试下两种风格的md）
2.1 map的初始化
map<string, string> number = {
pair<string, string>("123", "wuhan"),
pair<string, string>("hello", "shanghai"),
pair<string, string>("123", "wuhan"),
{
"345", "nanjing"},
{
"0755", "shenzhen"},
{
"8888", "shenzhen"}
};
2.2 map的遍历
for(auto &elem : number)
{
cout << elem.first << " " << elem.second << endl;
}
2.3 map的查找
cout <<endl;
size_t cnt1 = number.count("123");
size_t cnt2 = number.count("wuhan");
cout << "cnt1 = " << cnt1 << endl;
cout << "cnt2 = " << cnt2 << endl;
//或
auto it2 = number.find("123");
if(it2 == number.end())
{
cout << "该元素不存在map中" << endl;
}
else
{
cout << it2->first << " " << it2->second << endl;
}
cout << endl;
2.4 map的插入
//插入
/* pair<map<string, string>::iterator, bool> ret = */
/* number.insert(pair<string, string>("190", "xinjiang")); */
auto ret = number.insert({
"190", "xinjiang"});
if(ret.second)
{
cout << "插入成功" << ret.first->first
<< " " << ret.first->second << endl;
}
else
{
cout << "插入失败" << endl;
}
for(auto &elem : number)
{
cout << elem.first << " " << elem.second << endl;
}
2.5 map的下标访问
cout << endl;
cout << "number[\"123\"] = " << number["123"] << endl;
//查询key为9999的值，但是没value
cout << "number[\"9999\"] = " << number["9999"] << endl;
for(auto &elem : number)
{
cout << elem.first << " " << elem.second << endl;
}
cout << endl << endl;
//插入key为9999，value为beijing的值
number["9999"] = "beijing";
for(auto &elem : number)
{
cout << elem.first << " " << elem.second << endl;
}
cout << endl;
//修改map中key为123的value为beijing
/* number["123"] = "beijing"; */这句相当于下一句
number.operator[]("123").operator=("beijing");
for(auto &elem : number)
{
cout << elem.first << " " << elem.second << endl;
}
转载：https://blog.csdn.net/weixin_43679037/article/details/117043611