1. Two Sum

原题地址

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].

public class Solution {    public int[] twoSum(int[] nums, int target) {        Map<Integer,Integer> map = new HashMap<Integer,Integer>();        int[] result = new int[2];        int length = nums.length;        for(int i = 0; i < length; i++){            int diff = target-nums[i];            if(map.containsKey(diff)){                result[0] = map.get(diff);                result[1] = i;            }            map.put(nums[i],i);        }        return result;    }}