【leetcode】170. Two Sum III - Data structure design 两数之和之三 - 数据结构设计

　　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

class TwoSum {
public:
    void add(int number) {
        ++m[number];
    }
    bool find(int value) {
        for (auto a : m) {
            int t = value - a.first;
            if ((t != a.first && m.count(t)) || (t == a.first && a.second > 1)) {
                return true;
            }
        }
        return false;
    }
private:
    unordered_map<int, int> m;
};