# Map - 關聯容器

Map 是一種關聯數組的資料結構，也常被稱爲字典(dictionary)或鍵值對(key-value pair)。

## 程式實現

### Python

# map 在 python 中是一個keyword
hash_map = {} # or dict()
hash_map['shaun'] = 98
hash_map['wei'] = 99
exist = 'wei' in hash_map  # check existence
point = hash_map['shaun']  # get value by key
point = hash_map.pop('shaun') # remove by key, return value
keys = hash_map.keys()  # return key list
# iterate dictionary(map)
for key, value in hash_map.items():
# do something with k, v
pass


### C++

map<string, int> mp;
mp ["billryan"] = 69;
mp ["crossluna"] = 159;
auto it = mp.find("billryan");
if(it != mp.end()) {
// "billryan" found
cout << mp["billryan"]; // output: 69
}


### Java

Java 的實現中 Map 是一種將物件與物件相關聯的設計。常用的實現有HashMapTreeMap, HashMap被用來快速訪問，而TreeMap則保證『鍵』始終有序。Map 可以返回鍵的 Set, 值的 Collection, 鍵值對的 Set.

Map<String, Integer> map = new HashMap<String, Integer>();
map.put("bill", 98);
map.put("ryan", 99);
boolean exist = map.containsKey("ryan"); // check key exists in map
int point = map.get("bill"); // get value by key
int point = map.remove("bill") // remove by key, return value
Set<String> set = map.keySet();
// iterate Map
for (Map.Entry<String, Integer> entry : map.entrySet()) {
String key = entry.getKey();
int value = entry.getValue();
// do some thing
}