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
public class TwoSum { HashMap<Integer,Integer> map = new HashMap<Integer,Integer>(); // Add the number to an internal data structure. public void add(int number) { 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 key:map.keySet()) { int num1 = key; int num2 = value - num1; if(num1==num2&&map.get(num1)>1) return true; else if(num1!=num2&&map.containsKey(num2)) return true; } return false; } }
Two Sum III - Data structure design
原文：http://www.cnblogs.com/hygeia/p/5093141.html