1521. 找到最接近目标值的函数值

 参考https://space.bilibili.com/3203291/零神的题解

class Solution {
public:
    int closestToTarget(vector<int>& arr, int target) {
        int ans = abs(arr[0] - target);
        vector<int> valid = {arr[0]};
        for (int num: arr) {
            vector<int> validNew = {num};
            ans = min(ans, abs(num - target));
            for (int prev: valid) {
                validNew.push_back(prev & num);
                ans = min(ans, abs((prev & num) - target));
            }
            validNew.erase(unique(validNew.begin(), validNew.end()), validNew.end());
            valid = validNew;
        }
        return ans;
    }
};

class Solution {
    public int closestToTarget(int[] arr, int target) {
        HashSet<Integer> cur = new HashSet<>();
        int min = Integer.MAX_VALUE;
        for(int i : arr){
            HashSet<Integer> cur2 = new HashSet<>();
            cur2.add(i);
            min = Math.min(min,Math.abs(target-i));
            for(int j : cur){
                int val = j&i;
                cur2.add(val);
                min = Math.min(min,Math.abs(target-val));
            }
            cur = cur2;
        }
        return min;
    }
}