贴一下灵神的题解里面的解释~

就是一种优化策略，logtrick

class Solution {
public:
    int minimumDifference(vector<int>& nums, int k) {
        int res = 0x3f3f3f3f;
        int n = nums.size();
        for(int i=0;i<n;i++){
            res = min(res,abs(nums[i]-k));
            for(int j = i-1;j>=0&&(nums[j]|nums[i])!=nums[j];--j){
                nums[j] |= nums[i];
                res = min(res,abs(nums[j]-k));
            }
        }
        return res;
    };
};

同理换成AND的话就是看当前元素是不是前面的超集就好了

class Solution {
public:
    int closestToTarget(vector<int>& arr, int target) {
        int n = arr.size();
        int res = 0x3f3f3f3f;
        for(int i=0;i<n;i++){
            res = min(res,abs(target-arr[i]));
            for(int j=i-1;j>=0&&(arr[j]&arr[i])!=arr[j];--j){
                arr[j]&=arr[i];
                res = min(res,abs(target-arr[j]));
            }
        }
        return res;
    }
};