13.2 map

ゝ一世哀愁。 2022-05-13 09:24 111阅读 0赞

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> map<string,int> mp;
> 
> string name;
> 
> int score;
> 
> cin >> name >> score;
> 
> mp.insert(make\_pair(name,score));
> 
> cout << mp\["lily"\];//返回的是lily对应的score的值
> 
> 比如说：cin ： lily 78
> 
> 则cout: 78

#include<iostream>
    #include<map>
    using namespace std;
    int main()
    {
    	map<string,int> mp;
    	string name;
    	int score;
    	cin >> name >> score;
    	mp.insert(make_pair(name,score));
    	cout << mp["lily"] << endl;
    	return 0;
    }

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#include<iostream>
    #include<map>
    #include<string>
    using namespace std;
    
    struct Student{
    	string name;
    	int score;
    };
    
    Student s[5] = {
       {"Jack",89},{"jh",78},{"sd",54},{"sf",65},{"trr",90}};
    
    typedef map<string,int> MP;
    
    int main()
    {
    	MP mp;
    	for(int i = 0; i < 5; ++ i)
    		mp.insert(make_pair(s[i].name,s[i].score));
    	cout << mp["Jack"] << endl;//89
    	mp["jh"] = 90;
    	MP::iterator p;
    	for(p = mp.begin(); p != mp.end(); ++ p)
    		cout << p->first << " " << p->second << endl;
    	Student st;
    	st.name = "Jack";
    	st.score = 99;
    	pair<MP::iterator,bool> p2 = mp.insert(make_pair(st.name,st.score));
    	if(p2.second)//p.first为MP::iterator 
    	{
    		cout << p2.first->first << " " << p2.first->second << " " << "is inserted" << endl;
    	}
    	else
    		cout << "failed" << endl;
    	Student st2;
    	st2.name = "Ja";
    	st2.score = 99;
    	pair<MP::iterator,bool> p3 = mp.insert(make_pair(st2.name,st2.score));
    	if(p3.second)//p.first为MP::iterator 
    	{
    		cout << p3.first->first << " " << p3.first->second << "is inserted" << endl;
    	}
    	else
    		cout << "failed" << endl;
    	mp["Harry"] = 78;
    	MP::iterator q = mp.find("Harry");//查找的是关键字first
    	cout << q->first << " " << q->second << endl; 
    	return 0;	
    }

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> 本题主要是注意两个地方：
> 
> 1. 对出现的单词计数
> 
> 2. 对单词排序，排序规则为：先按次数多的输出，如果次数相等，按照字典序从小到大输出。
> 
> 对单词计数可以采用map对出现的单词进行计数，map<string,int> mp，关键字为string， mp\[s\]的值即为s对应的次数，刚开始默认为0.
> 
> 对单词排序，可以采用set，先将mp中的单词插入到set中，然后set按照排序规则输出即可。

#include<iostream>
    #include<map>
    #include<set>
    #include<string>
    using namespace std;
    
    struct Word{
    	int times;
    	string words;
    }; 
    
    struct rule{
    	bool operator()(const Word &a1, const Word &a2)
    	{
    		if(a1.times != a2.times) 
    			return a1.times > a2.times;
    		else
    			return a1.words < a2.words;
    	}
    };
    
    int main()
    {
    	freopen("13.4.txt","r",stdin);
    	map<string,int> mp;
    	set<Word,rule> st;
    	string s;
    	while(cin >> s)
    	{
    		++mp[s];//mp[s]返回的是与s对应的second，即int类型的次数，累计单词出现的次数 
    	}
    	map<string,int>::iterator p1;
    	for(p1 = mp.begin(); p1 != mp.end(); ++p1)//将mp中的数存在set中 (set中不含重复元素） 
    	{
    		Word a;
    		a.times = p1->second;
    		a.words = p1->first;
    		st.insert(a);
    	} 
    	set<Word,rule>::iterator p2;
    	for(p2 = st.begin(); p2 != st.end(); ++p2)//set按照rule规则排序后输出 
    		cout << p2->words << " " << p2->times << endl;
    	return 0; 
    }

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