1.map基本概念
简介:
- map中所有元素都是pair
- pair中的第一个元素为key(键值),起到索引作用,第二个元素为value(实值)
- 所有元素都会根据元素的键值自动排序
本质:
- map/multimap属于关联式容器,底层结构是用二叉树实现
优点:
- 可以根据key值快速找到value值
map和multimap的区别
- map不允许容器中有重复key元素
- multimap允许有重复key元素
2、map构造和赋值
函数原型:
- map<T1,T2> mp;map默认构造函数
- map(const map &mp);拷贝构造函数
- map& operator=(const map &mp);重载等号运算符
#include<map>
using namespace std;
void printmap(map<int, int> &mp)
{
for (map<int,int>::iterator it = mp.begin(); it != mp.end(); it++)
{
cout << (*it).first << " " << it->second << endl;
}
cout << endl;
}
void test01()
{
map<int, int> m;
m.insert(pair<int, int>(1, 10));
m.insert(pair<int, int>(2, 20));
m.insert(pair<int, int>(3, 25));
m.insert(pair<int, int>(4, 34));
m.insert(pair<int, int>(5, 23));
printmap(m);
map<int, int> m2(m);
printmap(m2);
map<int, int> m3;
m3 = m2;
printmap(m3);
}
int main()
{
test01();
system("pause");
return 0;
}
2、map大小和交换
函数原型:
- size();元素数目
- empty();是否为空
- sawp(mp);两个map交换元素
#include<map>
using namespace std;
void printmap(map<int, int> &mp)
{
for (map<int,int>::iterator it = mp.begin(); it != mp.end(); it++)
{
cout << (*it).first << " " << it->second << endl;
}
cout << endl;
}
void test01()
{
map<int, int> m;
m.insert(pair<int, int>(1, 10));
m.insert(pair<int, int>(2, 20));
m.insert(pair<int, int>(3, 25));
m.insert(pair<int, int>(4, 34));
m.insert(pair<int, int>(5, 23));
printmap(m);
cout << m.size() << endl;
map<int, int> m1;
m1.insert(pair<int, int>(3, 30));
m1.insert(pair<int, int>(5, 450));
m1.insert(pair<int, int>(7, 505));
m1.insert(pair<int, int>(6, 12));
m1.insert(pair<int, int>(9, 35));
printmap(m1);
m.swap(m1);
printmap(m);
printmap(m1);
}
int main()
{
test01();
system("pause");
return 0;
}
1 10
2 20
3 25
4 34
5 23
5
3 30
5 450
6 12
7 505
9 35
3 30
5 450
6 12
7 505
9 35
1 10
2 20
3 25
4 34
5 23
请按任意键继续. . .
4、map插入和删除
函数原型:
- insert(elem);
- clear();
- erase(pos); 删除pos迭代器所指的元素,返回下一个元素的迭代器
- erase(beg,end); 删除区间内所指的元素,返回下一个元素的迭代器
- erase(key);删除值为key的元素
#include <iostream>
#include <string>
#include <vector>
#include <ctime>
#include <cmath>
#include<fstream>
#include<algorithm>//标准算法头文件
#include<deque>
#include<stack>
#include<list>
#include<set>
#include<map>
using namespace std;
void printmap(map<int, int> &mp)
{
for (map<int,int>::iterator it = mp.begin(); it != mp.end(); it++)
{
cout << (*it).first << " " << it->second << endl;
}
cout << endl;
}
void test01()
{
map<int, int> m;
m.insert(pair<int, int>(1, 10));
m.insert(pair<int, int>(2, 20));
m.insert(pair<int, int>(3, 25));
m.insert(pair<int, int>(4, 34));
m.insert(pair<int, int>(5, 23));
m.insert(make_pair(8, 29));
m.insert(map<int, int>::value_type(12, 56));
m[17] = 89;//不建议用来插值,可以用来访问数据
cout << m[4] << endl;
printmap(m);
m.erase(m.begin());
printmap(m);
m.erase(3);
printmap(m);
m.erase(m.begin(), m.end());
printmap(m);
}
int main()
{
test01();
system("pause");
return 0;
}
34
1 10
2 20
3 25
4 34
5 23
8 29
12 56
17 89
2 20
3 25
4 34
5 23
8 29
12 56
17 89
2 20
4 34
5 23
8 29
12 56
17 89
请按任意键继续. . .
5、map查找与统计
函数原型:
- find(key);查找key是否存在,存在返回元素迭代器,不存在返回map.end();
- count(key);统计key的个数
#include <iostream>
#include <string>
#include <vector>
#include <ctime>
#include <cmath>
#include<fstream>
#include<algorithm>//标准算法头文件
#include<deque>
#include<stack>
#include<list>
#include<set>
#include<map>
using namespace std;
void printmap(map<int, int> &mp)
{
for (map<int,int>::iterator it = mp.begin(); it != mp.end(); it++)
{
cout << (*it).first << " " << it->second << endl;
}
cout << endl;
}
void test01()
{
map<int, int> m;
m.insert(pair<int, int>(1, 10));
m.insert(pair<int, int>(2, 20));
m.insert(pair<int, int>(3, 25));
m.insert(pair<int, int>(4, 34));
m.insert(pair<int, int>(5, 23));
m.insert(make_pair(8, 29));
m.insert(map<int, int>::value_type(12, 56));
printmap(m);
map<int, int>::iterator pos = m.find(2);
if (pos != m.end())
{
cout << pos->first << " " << (*pos).second << endl;
}
else {
cout << "没找到" << endl;
}
cout << m.count(4) << endl;
}
int main()
{
test01();
system("pause");
return 0;
}
1 10
2 20
3 25
4 34
5 23
8 29
12 56
2 20
1
请按任意键继续. . .
5、map排序
#include <iostream>
#include <string>
#include <vector>
#include <ctime>
#include <cmath>
#include<fstream>
#include<algorithm>//标准算法头文件
#include<deque>
#include<stack>
#include<list>
#include<set>
#include<map>
using namespace std;
void printmap(map<int, int> &mp)
{
for (map<int,int>::iterator it = mp.begin(); it != mp.end(); it++)
{
cout << (*it).first << " " << it->second << endl;
}
cout << endl;
}
class mycompare
{
public:
bool operator()(int v1, int v2)
{
return v1 > v2;
}
};
void test01()
{
map<int, int, mycompare> m;
m.insert(pair<int, int>(1, 10));
m.insert(pair<int, int>(6, 20));
m.insert(pair<int, int>(30, 25));
m.insert(pair<int, int>(13, 34));
m.insert(pair<int, int>(5, 23));
m.insert(make_pair(8, 29));
m.insert(map<int, int>::value_type(12, 56));
for (map<int, int,mycompare>::iterator it = m.begin(); it != m.end(); it++)
{
cout << (*it).first << " " << it->second << endl;
}
cout << endl;
}
int main()
{
test01();
system("pause");
return 0;
}
30 25
13 34
12 56
8 29
6 20
5 23
1 10
请按任意键继续. . .
案例:
#include <iostream>
#include <string>
#include <vector>
#include <ctime>
#include <cmath>
#include<fstream>
#include<algorithm>//标准算法头文件
#include<deque>
#include<stack>
#include<list>
#include<set>
#include<map>
using namespace std;
#define CHEHUA 0
#define YANFA 1
#define MEISHU 2
class worker
{
public:
string m_name;
int m_salsry;
};
void creatworker(vector<worker> &v)
{
string name = "ABCDEFGHIJ";
for (int i = 0; i < 10; i++)
{
worker worker;
worker.m_name = "员工";
worker.m_name += name[i];
worker.m_salsry = rand() % 10000 + 10000;
v.push_back(worker);
}
}
void setgroup(vector<worker> &v, multimap<int, worker> &m)
{
for (vector<worker>::iterator it = v.begin(); it != v.end(); it++)
{
int id = rand() % 3;
m.insert(make_pair(id, *it));
}
}
void showworker(multimap<int, worker> &m)
{
cout << "策划部门" << endl;
int count = m.count(CHEHUA);
int index = 0;
multimap<int, worker>::iterator pos = m.find(CHEHUA);
for (; pos != m.end() && index < count; pos++, index++)
{
cout << "姓名" << pos->second.m_name << " 工资" << pos->second.m_salsry << endl;
}
cout << "研发部门" << endl;
count = m.count(YANFA);
index = 0;
pos = m.find(YANFA);
for (; pos != m.end() && index < count; pos++, index++)
{
cout << "姓名" << pos->second.m_name << " 工资" << pos->second.m_salsry << endl;
}
cout << "美术部门" << endl;
count = m.count(MEISHU);
index = 0;
pos = m.find(MEISHU);
for (; pos != m.end() && index < count; pos++, index++)
{
cout << "姓名" << pos->second.m_name << " 工资" << pos->second.m_salsry << endl;
}
}
int main()
{
srand((unsigned int)time(NULL));
vector<worker> vworker;
creatworker(vworker);
multimap<int, worker> mworker;
setgroup(vworker, mworker);
showworker(mworker);
/*for (vector<worker>::iterator it = vworker.begin(); it != vworker.end(); it++)
{
cout << "姓名:" << it->m_name << " 工资:" << it->m_salsry << endl;
}*/
system("pause");
return 0;
}
策划部门
姓名员工F 工资16954
姓名员工H 工资16942
研发部门
姓名员工A 工资12572
姓名员工B 工资13740
姓名员工G 工资19223
姓名员工I 工资12946
美术部门
姓名员工C 工资12303
姓名员工D 工资14672
姓名员工E 工资12096
姓名员工J 工资11162
请按任意键继续. . .