## 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.

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
``````

Thoughts:

2. Find-favored algorithms

Code: algorithms that are Find-favored algorithms (TLE)

``````public class TwoSum {
Set<Integer> sum;
Set<Integer> num;

TwoSum(){
sum = new HashSet<Integer>();
num = new HashSet<Integer>();
}
// Add the number to an internal data structure.
if(num.contains(number)){
}else{
Iterator<Integer> iter = num.iterator();
while(iter.hasNext()){
}
}
}

// Find if there exists any pair of numbers which sum is equal to the value.
public boolean find(int value) {
return sum.contains(value);
}
}
``````

``````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, 2);
}
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) {
Iterator<Integer> iter = map.keySet().iterator();
while(iter.hasNext()){
int n1 = iter.next();
int n2 = value - n1;
if (map.containsKey(n2) &&(map.get(n2) == 2 || n1!=n2)){
return true;
}
}
return false;
}
}

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