Leetcode

Leetcode - Two Sum

问题描述

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].

算法实现

将值和下标存入Map，注意判断是否重复的情况

class Solution {
    public int[] twoSum(int[] nums, int target) {
        Map<Integer,Integer> map=new HashMap<>();
        for(int i=0;i<nums.length;i++)
            map.put(nums[i],i);
        for(int i=0;i<nums.length;i++){
            int t=target-nums[i];
            if(map.containsKey(t) && map.get(t)!=i){
                return new int[]{i,map.get(t)};
            }
        }
        return null;
    }
}