187. Repeated DNA sequence - with unordered_ Map basic content

class Solution {
    
public:
    vector<string> findRepeatedDnaSequences(string s) {
    
        unordered_map<string, int> map;
        vector<string> vecStr;
        if(s.size()<=10)    // The sample may not be longer than 10
            return vecStr;
        for(int i = 0; i <= s.size() - 10; i++){
        // Count the number of each occurrence 
            string str = s.substr(i, 10);
            if(map.find(str) != map.end())
                map.find(str)->second++;
            else{
    
                map.insert(pair<string, int>(str, 1));
            }
        }
        for (auto i = map.begin(); i != map.end(); i++){
        // The frequency of occurrence is greater than 1 Times added 
            if(i -> second > 1)
                vecStr.push_back(i -> first);
        }
        return vecStr;
    }
};

Accepted
31/31 cases passed (44 ms)
Your runtime beats 77.64 % of cpp submissions
Your memory usage beats 23.79 % of cpp submissions (22.9 MB)

unordered_map The iterator of is a pointer , Point to this element , Get its value through an iterator .

1 unordered_map<Key,T>::iterator it; 
2 (*it).first;             // the key value (of type Key)
3 (*it).second;            // the mapped value (of type T)
4 (*it);                   // the "element value" (of type pair<const Key,T>) 

Its key values are iterator's first and second attribute .

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

Member functions ：

================= iterator =========================
begin 　　 Returns the iterator pointing to the beginning of the container （iterator）
end 　　 The position of the iterator at the end of the container points to
cbegin　 Returns a constant iterator pointing to the beginning of the container （const_iterator）
cend 　　 Returns the constant iterator pointing to the end of the container
================= Capacity ================
size 　　 Returns the number of valid elements
max_size return unordered_map The maximum number of elements supported
empty Determine whether it is null
================= Element access =================
operator[] 　　 Access elements
at 　　 　　　　 Access elements
================= Element modification =================
insert 　　 Insert elements
erase　　 Remove elements
swap 　　 Exchange content
clear　　 Empty content
emplace 　 Construct and insert an element
emplace_hint Follow the prompts to construct and insert an element
================ operation =========================
find 　　　　　　 Find elements by giving a primary key , Did not find ： return unordered_map::end
count 　　　　　 Returns the number of elements that match a given primary key
equal_range 　　 The return value matches the range of elements of a given search value
================ Buckets ======================
bucket_count 　　　 Return slot （Bucket） Count
max_bucket_count Returns the maximum number of slots
bucket_size 　　　 Return slot size
bucket 　　　　　　 Returns the serial number of the slot where the element is located
load_factor　　　　 Returns the load factor , It's an element tank （Bucket） The maximum number of elements
max_load_factor 　 Returns or sets the maximum load factor
rehash　　　　　　 Set the number of slots
reserve 　　　　　 Request to change container capacity