[leetcode 刷题记录] 170. Two Sum III - Data structure design

170. Two Sum III - Data structure design

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.

For example,

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

这个solution用到了multiset，multisite允许set中出现重复元素

class TwoSum {
public:

// Add the number to an internal data structure.
void add(int number) {
nums.insert(number);
}

// Find if there exists any pair of numbers which sum is equal to the value.
bool find(int value) {
for (auto n: nums) {
int count = value - n == n ? 2 : 1;
if (nums.count(value - n) >= count) return true;
}
return false;
}
private:
unordered_multiset<int> nums;
};