LeetCode-TwoSum

题目描述：

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.

Example:

Given nums = [2, 7, 11, 15], target = 9,Because nums[0] + nums[1] = 2 + 7 = 9,return [0, 1].

本题考虑用Hash来解，代码如下：

public class Solution {
    public int[] twoSum(int[] nums, int target) {
          HashMap<Integer,Integer> map = new HashMap<Integer,Integer>();
          for(int i = 0;i<nums.length;i++){
              map.put(nums[i],i);     //将读入的数据加入到map中
          }
          int  index1 = 0;
          int  index2 = 0;
          for(int i = 0;i < nums.length;i++){
              index1 = i;
              int find = target - nums[index1];       
              if(map.get(find) != null && map.get(find) != index1){    //判断是否满足条件
                  index2 = map.get(find);       //满足条件将该值赋给index2
                  break;
              }
          }
          int[] res = new int[2];
          res[0] = index1<index2?index1:index2;
          res[1] = index1>index2?index1:index2;
          return res;      //返回两个元素的下标，下标从1开始
    }
}