LeetCode第一道题---Two Sum

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.

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Example:

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

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

分析

将数组放入HashMap中，然后遍历数组，如果目标值-num等于数组中的另一个值时，并且不是本值，那么这两个值就是我们需要的值。

class Solution {
    public int[] twoSum(int[] nums, int target) {
        int[] answer=new int[2];
        HashMap<Integer,Integer> map=new HashMap();
      for(int i=0;i<nums.length;i++){
          map.put(nums[i],i);
      }  
        for(int j=0;j<nums.length;j++){
            int b=target-nums[j];
            if(map.containsKey(b)&&j!=map.get(b)){
                return new int[]{j,map.get(b)};
            }
        }
        return answer;
    }
}