Question:
Design and implement a TwoSum class. It should support the following operations: add and find.
add(input) – Add the number input to an internal data structure.
find(value) – 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
我们把每个数字和其出现的次数建立映射，然后遍历哈希表，对于每个值，我们先求出此值和目标值之间的差值t，然后分两种情况来看，如果当前值不等于差值t，那么只要哈希表中有差值t就返回True，或者是当差值t等于当前值时，如果此时哈希表的映射次数大于1，则表示哈希表中还有另一个和当前值相等的数字，二者相加就是目标值。
class TwoSum {
private:
unordered_map<int,int> table;
public:
void add(int number) {
table[number]++;
}
bool find(int value) {
for(auto elem : table)
{
for (vector<string>::iterator i = v.begin(); i != v.end(); ++i);
for (auto i = v.begin(); i != v.end(); ++i);
int num1 = elem.second;
int num2 = value == (elem.first << 1) ? num1 - 1 : buffer.find(value - elem.first) != buffer.end();
if(num1 && num2){
return true;
}
}
return false;
}
};
leetcode3 Two Sum III – Data structure design
原文：http://www.cnblogs.com/whowhoha/p/5743283.html