2017-08-19 10:58:52
writer;pprp
#include <map>
#include <string>
#include <iostream>
#include <vector>
#include <algorithm> using namespace std;
typedef pair<int, string> PAIR; ostream & operator<<(ostream & out, const PAIR& p)
{
out << p.first << " " << p.second << endl;
return out;
} //函数对象，对（）进行了重载
struct CmpByValue
{
bool operator()(const PAIR&l, const PAIR&r)
{
return l.second < r.second;
}
}; int main()
{
//数据插入
map<int, string> mapStudent; mapStudent.insert(map<int, string>::value_type (, "student_one"));
mapStudent.insert(map<int, string>::value_type (, "student_two"));
mapStudent.insert(map<int, string>::value_type (, "student_three"));
mapStudent.insert(map<int, string>::value_type (,"student_four"));
mapStudent.insert(pair<int, string>(, "student_six"));
mapStudent.insert(make_pair(, "student_seven"));
mapStudent[] = "student_five"; //数据遍历
//正向遍历
map<int, string>::iterator iter;
for(iter = mapStudent.begin(); iter != mapStudent.end(); iter++)
{
cout<<iter->first<<" "<<iter->second<<endl;
}
//反向遍历
map<int, string>::reverse_iterator it;
for(it = mapStudent.rbegin(); it != mapStudent.rend() ; it++)
{
cout << it->first <<" " << it->second << endl;
}
//数组形式的遍历
int nSize = mapStudent.size();
for(int i = ; i < nSize ; i++)
{
cout << mapStudent[i] << endl;
}
cout << endl; //数据的查找
map<int, string>::iterator iter1; iter1 = mapStudent.find(); if(iter1 != mapStudent.end())
{
cout << iter1->second << endl;
}
else
{
cout << "can't find it " << endl;
} //判断是否存在这个key
int judge = mapStudent.count(); if(judge)
{
cout << "exist" << endl;
}
else
{
cout << "not exist" << endl;
} cout << endl; //用lower_bound进行查找
map<int, string> :: iterator it2;
it2 = mapStudent.lower_bound();
cout << it2->second << endl;
it2 = mapStudent.upper_bound();
cout << it2->second << endl; pair<map<int, string>::iterator, map<int, string>::iterator> mapair;
mapair = mapStudent.equal_range();
//如果相等的话那就说明没有找到，如果不等就说明找到了
if(mapair.first == mapair.second)
cout << "can't find it" << endl;
else
cout << "the value of it is " << mapair.first->second << endl; //数据的清空与判空
// mapStudent.clear();
if(!mapStudent.empty())
cout << "not empty" << endl;
else
cout << "empty" << endl; //数据的删除
map<int, string> :: iterator it3;
it3 = mapStudent.find();
mapStudent.erase(it3); for(it3 = mapStudent.begin(); it3 != mapStudent.end(); it3++)
cout << it3->second << endl; judge = mapStudent.erase();
if(judge)
{
cout << "delete successfully" << endl;
for(it3 = mapStudent.begin(); it3 != mapStudent.end(); it3++)
{
cout << it3->second << endl;
}
} //排序（按照key的大小排序）
//map<int, string, less<int> >是默认的升序
//map<int, string, greater<int> >是可以构造的降序 //排序（按照value的大小排序）
vector <PAIR> sortByValue(mapStudent.begin(), mapStudent.end()); sort(sortByValue.begin(), sortByValue.end(),CmpByValue()); for(int i = ; i < mapStudent.size(); i++)
{
cout << sortByValue[i]<< endl;
}
return ;
}
另外multimap用法与map类似，函数什么的都一样，只是支持一个key对多个value
/*
name : usage of List
writer : pprp
declare : null
date ； 2017/8/20
*/
#include <bits/stdc++.h> using namespace std; void print(multimap<string,double>&k)
{
multimap<string, double>::iterator it;
for(it = k.begin(); it != k.end() ; it++)
{
cout << it->first << " " << it->second << endl;
}
} int main()
{
multimap<string, double>mp;
mp.insert(pair<string,double>("jack",300.23));
mp.insert(make_pair("green",234.1));
mp.insert(make_pair("red",234.132));
mp.insert(make_pair("yellow",2342.1));
mp.insert(make_pair("blue",234.11));
mp.insert(make_pair("orange",2324.1)); multimap<string, double>::iterator it; print(mp); mp.erase("jack"); print(mp); it = mp.find("orange");
if(it != mp.end())
{
cout << it->first << " " << it->second << endl;
} return ;
}