leetcode 001 Tow Sum(java)

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

 

提议：输入一个数组 和 一个目标数，数组中有两个数相加和为目标数，输出这两个数的下标且下标数小的先输出。

题解： 用了JAVA的hashmap。不是很会用。

import java.util.HashMap;
import java.util.Map;


public class Solution {
    public static int[] twoSum(int[] nums, int target) {
      int[] res =new int[2];
      
      HashMap<Integer, Integer> map =new HashMap<Integer, Integer>();
      for(int i=0;i<nums.length;i++){
          if(!map.containsKey(target-nums[i])){
              map.put(nums[i], i);
          }
          else{
              res[0]=map.get(target-nums[i])+1;
              res[1]=i+1;
              break;
          }
      }
      return res;
 }
    
    public static void main(String[] args) {
        int[] nums=new int[]{1,5,5,10};
        int[] res=new int[2];
        res=twoSum(nums,10);
        System.out.println(res[0]+" "+res[1]);
    }
    
    
}