《算法图解》chap5 散列表

 1 voted={}
 2 def check_voter(name):
 3     #如果有人要投票，投过了就不给投，否则就让他们投
 4     if voted.get(name):
 5         #先判断有没有在voted里面，如果没有就存进去并且允许投票
 6         
 7         print("kick them out")
 8     else :
 9         voted[name]=True
10         print ("let them vote!")
11 
12 check_voter("tom")
13 check_voter("tom")

1 it->first;               // same as (*it).first   (the key value)
2 it->second;               //same as (*it).second   (the mapped value)

#include <iostream>
#include <unordered_map>
//使用散列表时需要包含此散列表<unordered_map>
#include <string>
using namespace std;


unordered_map<string, bool> voted;
//定义一个散列表名为voted，用于储存已经投过票的人的名字，其中键是字符串类型，值是bool类型

void check_voter(const string& name) {
    //检查该名字是否投过票，没有投票就投票并保存，有就不允许投票
    auto search = voted.find(name);
    //自动定义类型；find（）是通过给定主键查找元素,没找到：返回unordered_map::end
    if (search == voted.end() || search->second == false) {
        //没找到或者找到了但是值是false, search->second(the same as (*search).second）就插入
        voted.insert({ name, true });
        //
        cout << "Let them vote!" << endl;;
    }
    else {
        cout << "Kick them out!" << endl;
    }
}

int main() {
    check_voter("tom");
    check_voter("mike");
    check_voter("mike");
}

 1 #include <utility>
 2 using namespace std;
 3 
 4 using std::cout;
 5 using std::endl;
 6 
 7 int main() {
 8     std::unordered_map<std::string, float> book = {
 9         {"apple", 0.67},
10         {"milk", 1.49},
11         {"avocado", 1.49}
12     };
13     //初始化一个散列表
14 
15     // print book
16     for (std::pair<std::string, float> pair : book) {
17         //pair：objects that can hold two values of different types 
18         cout << pair.first << ": " << pair.second << "$" << endl;
19     }
20     //print book遍历的三种方式
21     for (auto it = book.begin(); it != book.end(); ++it)
22     {
23         cout << it->first << ":" << it->second<<"$"<<endl;
24     }
25     for (auto it = book.begin(); it != book.end(); it++)
26     {
27         cout << (*it).first << ":" << (*it).second << "$" << endl;
28     }
29          
30   
31     
32 }