import java.util.Arrays;

/**
 * 給定有序陣列arr，代表X軸上的點，給定一個正整數K，代表長度為K的繩子，問繩子最多能蓋住幾個點(繩子邊緣碰到也算蓋住)
 * <p>
 * 滑動視窗
 */
public class CoverMostPoint {

    public static int coverMostPoint(int[] arr, int k) {
        int left = 0;
        int right = 0;
        int max = 0;
        int length = arr.length;
        while (left < length) {
            while (right < length && arr[right] - arr[left] <= k) {
                right++;
            }
            max = Math.max(max, right - left);
            left++;
        }
        return max;
    }

    public static int coverMostPoint2(int[] arr, int L) {
        int res = 1;
        for (int i = 0; i < arr.length; i++) {
            int nearest = nearestIndex(arr, i, arr[i] - L);
            res = Math.max(res, i - nearest + 1);
        }
        return res;
    }

    public static int nearestIndex(int[] arr, int R, int value) {
        int L = 0;
        int index = R;
        while (L <= R) {
            int mid = L + ((R - L) >> 1);
            if (arr[mid] >= value) {
                index = mid;
                R = mid - 1;
            } else {
                L = mid + 1;
            }
        }
        return index;
    }

    // for test
    public static int test(int[] arr, int L) {
        int max = 0;
        for (int i = 0; i < arr.length; i++) {
            int pre = i - 1;
            while (pre >= 0 && arr[i] - arr[pre] <= L) {
                pre--;
            }
            max = Math.max(max, i - pre);
        }
        return max;
    }

    // for test
    public static int[] generateArray(int len, int max) {
        int[] ans = new int[(int) (Math.random() * len) + 1];
        for (int i = 0; i < ans.length; i++) {
            ans[i] = (int) (Math.random() * max);
        }
        Arrays.sort(ans);
        return ans;
    }

    public static void main(String[] args) {
        int len = 100;
        int max = 1000;
        int testTime = 100000;
        System.out.println("測試開始");
        for (int i = 0; i < testTime; i++) {
            int k = (int) (Math.random() * max);
            int[] arr = generateArray(len, max);
            int ans1 = coverMostPoint(arr, k);
            int ans2 = coverMostPoint2(arr, k);
            int ans3 = test(arr, k);
            if (ans1 != ans2 || ans2 != ans3) {
                System.out.println("oops!");
                break;
            }
        }
        System.out.println("測試結束");

    }

}

/* 如有意見或建議，歡迎評論區留言；如發現程式碼有誤，歡迎批評指正 */