Easy 170题 Two Sum III - Data structure design

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最新推荐文章于 2024-03-31 12:09:16 发布

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设计一个TwoSum类，实现添加数字到内部数据结构，并判断是否存在两数之和等于特定值的功能。类需支持add和find两个操作。

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Question:

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

Solution:

public class TwoSum {
    private List<Integer> ans=new ArrayList<Integer>();
    private Map<Integer, Integer> map= new HashMap<Integer,Integer>();
    // Add the number to an internal data structure.
	public void add(int number) {
	    ans.add(number);
	}

    // Find if there exists any pair of numbers which sum is equal to the value.
	public boolean find(int value) {
	    for(int i=0;i<=ans.size()-1;i++)
	    {
	        if(map.containsKey(value-ans.get(i))&&i!=map.get(value-ans.get(i)))
	            return true;
	        else
	            map.put(ans.get(i),i);
	    }
	    return false;
	}
}


// Your TwoSum object will be instantiated and called as such:
// TwoSum twoSum = new TwoSum();
// twoSum.add(number);
// twoSum.find(value);

发觉没有根据value找key的方法