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## Problem

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:

find(4) -> true
find(7) -> false

Example 2:

find(3) -> true
find(6) -> false

## Code

class TwoSum {
private HashMap<Integer, Integer> map;
/** Initialize your data structure here. */
public TwoSum() {
map = new HashMap<>();
}

/** Add the number to an internal data structure.. */
if(map.containsKey(number)){
map.put(number, map.get(number) + 1);
} else {
map.put(number, 1);
}
}

/** Find if there exists any pair of numbers which sum is equal to the value. */
public boolean find(int value) {
for(Map.Entry<Integer, Integer> entry : map.entrySet()){
int num1 = entry.getKey();
int comp = value - num1;
if((num1 == comp) && entry.getValue() > 1
|| (num1 != comp) && map.containsKey(comp)){
return true;
}
}

return false;
}
}

/**
* Your TwoSum object will be instantiated and called as such:
* TwoSum obj = new TwoSum();