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
一刷
题解：
用map来保存value和1表示出现1次，2表示出现2次。寻找的时候。遍历map的key，然后判断value - key在不在map中
public class TwoSum {
Map<Integer, Integer> hm;
/** Initialize your data structure here. */
public TwoSum() {
hm = new HashMap<>();
}
/** Add the number to an internal data structure.. */
public void add(int number) {
if(hm.containsKey(number)) hm.put(number, 2);
else hm.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 = hm.keySet().iterator();
while(iter.hasNext()){
int num1 = iter.next();
int num2 = value - num1;
if(hm.containsKey(num2)){
if(num1 != num2 || hm.get(num2) == 2) return true;
}
}
return false;
}
}
/**
* Your TwoSum object will be instantiated and called as such:
* TwoSum obj = new TwoSum();
* obj.add(number);
* boolean param_2 = obj.find(value);
*/
