LeetCode刷题之TWO_SUM_0001

java版本：

 public static void main(String[] args) {
    int[] nums = {-1,-2,-3,-4,-5};
    int[] sum = twoSum(nums, -8);
    System.out.println(Arrays.toString(sum));
  }

//方法一，暴力破解 试图用过滤条件减少循环次数 为什么不换一种方式？
 public static int[] twoSum(int[] nums, int target) {

    int[] reNums = new int[2];
    for (int i = 0; i < nums.length;i++) {
        //if(target - nums[i] >= 0){
          for (int j = i + 1; j < nums.length; j++) {
              //if(target -nums[i] - nums[j] < 0) continue;
              if((nums[i] + nums[j]) == target){
                  reNums[0] = i;
                  reNums[1] = j;
                  break;
              }
          }
        //}
    }
    return reNums;
}
//第二种方式：哈希表 HashMap
 public static int[] twoSum_hash(int[] nums, int target) {
        Map<Integer,Integer> map = new HashMap<>();
        for (int i = 0; i < nums.length; i++) {
            int tempR = target - nums[i];
           if(map.containsKey(tempR)){
               return new int[]{map.get(tempR),i};
           }
           map.put(nums[i],i);
        }
        return null;
  }