# 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.

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
``````
``````public class TwoSum {
Map<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 (int i : map.keySet()) {
int target = value - i;

if (map.containsKey(target)) {
if (target != i) {
return true;
} else {
if (map.get(i) > 1) {
return true;
}
}
}
}

return false;
}
}

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