170. Two Sum III - Data structure design ----E

Design and implement a TwoSum class. It should support the following operations: add and find.

add - Add the number to an internal data structure.
find - Find if there exists any pair of numbers which sum is equal to the value.

Example 1:

add(1); add(3); add(5);
find(4) -> true
find(7) -> false

Example 2:

add(3); add(1); add(2);
find(3) -> true
find(6) -> false

A:
用HashMap, save with count

class TwoSum {
public:
    /** Initialize your data structure here. */
    TwoSum() {
        
    }
    
    /** Add the number to an internal data structure.. */
    void add(int number) {
        M[number]++;
    }
    
    /** Find if there exists any pair of numbers which sum is equal to the value. */
    bool find(int value) {
        auto iter = M.begin();
        while(iter!=M.end()){
            int key = iter->first;
            int count = iter->second;
            if(key == value - key){
                if(count>1)
                    return true;
            }else{
                if(M.find(value - key) != M.end()){
                    return true;
                }
            }
            iter++;
        }
        return false;
    }
private:
    unordered_map<int,int> M; // value and its count
};

/**
 * Your TwoSum object will be instantiated and called as such:
 * TwoSum* obj = new TwoSum();
 * obj->add(number);
 * bool param_2 = obj->find(value);
 */

Mistakes:

1： 开始根本没有考虑重复的情况。
   上来就用了Set
 哎，就是自己SB， 没办法， 水平不够，  Tiger
是根本的人的问题，   再刷1000遍也没办法的，Tiger

艹