【每日一题Day163】LC2367算术三元组的数目 | 二分查找 哈希表

class Solution {
    public int arithmeticTriplets(int[] nums, int diff) {
        int res = 0;
        for (int i = 0; i < nums.length; i++){
           if (binarySearch(nums, nums[i] + diff) != -1 && binarySearch(nums, nums[i] + 2 * diff) != -1){
               res++;
           }           
        }
        return res;
    }
    public int binarySearch(int[] nums, int target){
        int l = 0, r = nums.length - 1;
        while (l <= r){
            int mid = (l + r) >> 1;
            if (nums[mid] == target){
                return mid;
            }else if (nums[mid] > target){
                r = mid - 1;
            }else{
                l = mid + 1;
            }
        }
        return -1;
    }
}

class Solution {
    public int arithmeticTriplets(int[] nums, int diff) {
        Set<Integer> set = new HashSet<>();
        int res = 0;
        for (int i = 0; i < nums.length; i++){
           if (set.contains(nums[i] - diff) && set.contains(nums[i] - 2 * diff)){
               res++;
           }      
           set.add(nums[i]);
        }
        return res;
    }
}