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Given an array of integers, return indices of the two numbers such that they add up to a specific target.

You may assume that each input would have exactly one solution, and you may not use the same element twice.

Example:

Given nums = [2, 7, 11, 15], target = 9,

Because nums[0] + nums[1] = 2 + 7 = 9,

return [0, 1].

我的思路

class Solution {
       public int[] twoSum(int[] nums, int target) {
           int[] res = new int[2];        if(nums == null || nums.length <= 1) return res;        HashMap
   
     map = new HashMap
    
     ();        for(int i = 0; i < nums.length; i++){
               int val = target - nums[i];            if(map.containsKey(val) && map.get(val) != i){
                   res[0] = i;                res[1] = map.get(val);                return res;            }else map.put(nums[i], i);        }        return res;    }}
    
   

2019.12.17 update:

public class Solution {
       public int[] twoSum(int[] numbers, int target) {
           Arrays.sort(numbers);        int L = 0, R = numbers.length - 1;        while (L < R) {
               if (numbers[L] + numbers[R] == target) {
                   int[] pair = new int[2];                pair[0] = numbers[L];                pair[1] = numbers[R];                return pair;            }            if (numbers[L] + numbers[R] < target) {
                   L++;            } else {
                   R--;            }        }        return null;    }}

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