Floor and Ceil in Sorted Array in DSA Javascript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to find the floor value in a sorted array.

DSA Javascript

function findFloor(arr, target) {
  let low = 0, high = arr.length - 1;
  let floor = -1;
  while (low <= high) {
    let mid = Math.floor((low + high) / 2);
    if (arr[mid] === target) {
      return arr[mid];
    } else if (arr[mid] < target) {
      floor = arr[mid];
      low = [1];
    } else {
      high = mid - 1;
    }
  }
  return floor;
}

Drag options to blanks, or click blank then click option'

Alow + 1

Bmid + 1

Cmid - 1

Dhigh - 1

Attempts:

3 left

💡 Hint

Common Mistakes

Setting low to mid - 1 instead of mid + 1 causes infinite loop or wrong result.

Updating high instead of low when arr[mid] < target.

When arr[mid] is less than target, we move low to mid + 1 to search the right half.

2fill in blank

medium

Complete the code to find the ceil value in a sorted array.

DSA Javascript

function findCeil(arr, target) {
  let low = 0, high = arr.length - 1;
  let ceil = -1;
  while (low <= high) {
    let mid = Math.floor((low + high) / 2);
    if (arr[mid] === target) {
      return arr[mid];
    } else if (arr[mid] > target) {
      ceil = arr[mid];
      high = [1];
    } else {
      low = mid + 1;
    }
  }
  return ceil;
}

Drag options to blanks, or click blank then click option'

Amid - 1

Blow - 1

Chigh + 1

Dmid + 1

Attempts:

3 left

💡 Hint

Common Mistakes

Setting high to mid + 1 instead of mid - 1 causes wrong search direction.

Updating low instead of high when arr[mid] > target.

When arr[mid] is greater than target, we move high to mid - 1 to search the left half.

3fill in blank

hard

Fix the error in the binary search loop condition to avoid infinite loops.

DSA Javascript

function binarySearch(arr, target) {
  let low = 0, high = arr.length - 1;
  while (low [1] high) {
    let mid = Math.floor((low + high) / 2);
    if (arr[mid] === target) {
      return mid;
    } else if (arr[mid] < target) {
      low = mid + 1;
    } else {
      high = mid - 1;
    }
  }
  return -1;
}

Drag options to blanks, or click blank then click option'

A<=

B<

C>=

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' causes missing the last element and possibly wrong results.

Using '>' or '>=' reverses the logic and causes no iterations.

The loop should continue while low is less than or equal to high to cover all elements.

4fill in blank

hard

Fill both blanks to create a function that returns both floor and ceil values for a target in a sorted array.

DSA Javascript

function findFloorAndCeil(arr, target) {
  let low = 0, high = arr.length - 1;
  let floor = -1, ceil = -1;
  while (low <= high) {
    let mid = Math.floor((low + high) / 2);
    if (arr[mid] === target) {
      floor = arr[mid];
      ceil = arr[mid];
      break;
    } else if (arr[mid] < target) {
      floor = arr[mid];
      low = [1];
    } else {
      ceil = arr[mid];
      high = [2];
    }
  }
  return { floor, ceil };
}

Drag options to blanks, or click blank then click option'

Amid + 1

Bmid - 1

Clow + 1

Dhigh - 1

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping low and high updates causes infinite loops.

Using low + 1 or high - 1 incorrectly without mid causes wrong results.

When arr[mid] < target, move low to mid + 1; when arr[mid] > target, move high to mid - 1.

5fill in blank

hard

Fill all three blanks to create a function that returns floor and ceil using a single pass binary search.

DSA Javascript

function floorAndCeil(arr, target) {
  let low = 0, high = arr.length - 1;
  let floor = -1, ceil = -1;
  while (low <= high) {
    let mid = Math.floor((low + high) / 2);
    if (arr[mid] === target) {
      floor = arr[mid];
      ceil = arr[mid];
      break;
    } else if (arr[mid] < target) {
      floor = arr[mid];
      low = [1];
    } else {
      ceil = arr[mid];
      high = [2];
    }
  }
  return { [3] };
}

Drag options to blanks, or click blank then click option'

Amid + 1

Bmid - 1

Cfloor, ceil

Dlow, high

Attempts:

3 left

💡 Hint

Common Mistakes

Returning low and high instead of floor and ceil.

Incorrect pointer updates causing infinite loops.

Update low to mid + 1, high to mid - 1, and return floor and ceil as an object.