Two Sum 数组中找两个之和为sum@LeetCode

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原创最新推荐文章于 2026-05-02 14:00:34 发布 2.9k 阅读 AI 写同款· GEO 优化 ›

电面：给一个数组找出和为k的两个数如标题所述，其实LeetCode上也有道差不多的题，Two Sum返回这两个数的对应下标。那我就按LeetCode上那道题来写吧。先用双指针的方法嘛，不过LeetCode上面是要求返回下标，那么就不能用sort直接对原本的数组进行排序，会影响之前本来的下标。所以得先复制一个数组出来。双指针没什么好说的，因为已经排好序了，一个从最左端走，一个从最右端走。写这个主要是为学习一下C中的qsor 阅读详情

思路：

用Hashtable，遍历数组时对每个数边放边查找

package Level2;

import java.util.HashMap;
import java.util.Hashtable;

/**
 * Two Sum
 * 
 * Given an array of integers, find two numbers such that they add up to a specific target number.

The function twoSum should return indices of the two numbers such that they add up to the target, where index1 must be less than index2. Please note that your returned answers (both index1 and index2) are not zero-based.

You may assume that each input would have exactly one solution.

Input: numbers={2, 7, 11, 15}, target=9
Output: index1=1, index2=2
 */
public class S1 {

	public static void main(String[] args) {
		Hashtable<Integer, Integer> ht = new Hashtable<Integer, Integer>();
		System.out.println(ht.get(22));
	}

	public int[] twoSum(int[] numbers, int target) {
		// 放值和数组下标
		Hashtable<Integer, Integer> ht = new Hashtable<Integer, Integer>();
		int[] ret = new int[2];
		
		for(int i=0; i<numbers.length; i++){
			// 对每一个数边放边查找
			if(ht.get(target-numbers[i]) != null){
				ret[0] = ht.get(target-numbers[i]) + 1;
				ret[1] = i+1;
			}else{
				ht.put(numbers[i], i);
			}
		}
		
		return ret;
	}
}

import java.util.*;
public class Solution {
    public int[] twoSum(int[] numbers, int target) {
        Hashtable<Integer, Integer> ht = new Hashtable<Integer, Integer>();
        int[] ret = {0,0};
        for(int i=0; i<numbers.length; i++) {
            Integer index = ht.get(target-numbers[i]);
            if(index != null) {
                ret[0] = index+1;
                ret[1] = i+1;
            }
            ht.put(numbers[i], i);
        }
        return ret;
    }
}

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