Meeting Rooms Problem Minimum Rooms Required in DSA C - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare the variable that stores the number of meeting rooms needed.

DSA C

int [1] = 0;

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

AmaxRooms

Bcount

Cintervals

Drooms

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'intervals' which is usually the input array.

Using 'count' which is too generic.

The variable maxRooms is used to keep track of the minimum number of rooms required.

2fill in blank

medium

Complete the code to sort the start times of meetings.

DSA C

qsort(start, n, sizeof(int), [1]);

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AcompareInts

BcompareIntervals

CcompareStart

Dcompare

Attempts:

3 left

💡 Hint

Common Mistakes

Using a comparator meant for intervals instead of integers.

The function compareInts is used to sort integer arrays like start times.

3fill in blank

hard

Fix the error in the loop that checks overlapping meetings.

DSA C

for (int i = 1; i < n; i++) {
    if (start[i] < [1]) {
        rooms++;
    } else {
        endIndex++;
    }
}

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Astart[endIndex]

Bend[i]

Cstart[i-1]

Dend[endIndex]

Attempts:

3 left

💡 Hint

Common Mistakes

Comparing start times instead of end times.

Using wrong indices.

We compare the current start time with the earliest end time end[endIndex] to check overlap.

4fill in blank

hard

Fill both blanks to correctly update the number of rooms and the end index.

DSA C

if (start[i] < end[[1]]) {
    [2]++;
} else {
    endIndex++;
}

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

AendIndex

Brooms

Ci

Dcount

Attempts:

3 left

💡 Hint

Common Mistakes

Incrementing the wrong variable.

Using wrong indices for comparison.

Compare start[i] with end[endIndex]. If overlapping, increase rooms count.

5fill in blank

hard

Fill all three blanks to create a dictionary of meeting start times and their counts for overlap.

DSA C

for (int i = 0; i < n; i++) {
    countMap[[1]] = countMap[[2]] + [3];
}

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

Astart[i]

C1

Dend[i]

Attempts:

3 left

💡 Hint

Common Mistakes

Using end[i] as key.

Adding wrong increment value.

We use start[i] as key to countMap and add 1 to increment count.

Practice

1. What does the "Meeting Rooms Problem Minimum Rooms Required" ask you to find given a list of meeting time intervals?

easy

A. The minimum number of meeting rooms needed to hold all meetings without overlap

B. The maximum duration of a single meeting

C. The total number of meetings scheduled

D. The earliest start time among all meetings

Solution

1. Step 1: Understand the problem goal

   The problem asks for the minimum number of rooms needed so that no two meetings overlap in the same room.

2. Step 2: Clarify what is asked

   We want to find how many rooms are needed to schedule all meetings without time conflicts.

3. Final Answer:

   The minimum number of meeting rooms needed to hold all meetings without overlap -> Option A

4. Quick Check:

   Minimum rooms = no overlapping meetings at the same time [OK]

Hint: Count max overlapping meetings to find minimum rooms [OK]

Common Mistakes:

• Confusing total meetings with rooms needed
• Thinking about meeting durations instead of overlaps
• Ignoring overlapping intervals

2. Which of the following C code snippets correctly declares an array of meeting intervals where each interval has a start and end time?

easy

A. int intervals[2][3] = {{0, 5, 15}, {30, 10, 20}};

B. int intervals[3] = {0, 30, 5, 10, 15, 20};

C. int intervals[3][2] = {0, 30, 5, 10, 15, 20};

D. int intervals[3][2] = {{0, 30}, {5, 10}, {15, 20}};

Solution

1. Step 1: Check array dimensions and initialization

   We need a 2D array with 3 intervals, each having 2 values (start and end).

2. Step 2: Validate each option

   int intervals[3][2] = {{0, 30}, {5, 10}, {15, 20}}; correctly declares int intervals[3][2] with proper nested braces for each interval.

3. Final Answer:

   int intervals[3][2] = {{0, 30}, {5, 10}, {15, 20}}; -> Option D

4. Quick Check:

   Correct 2D array syntax for intervals [OK]

Hint: Use int arr[n][2] for intervals with start and end [OK]

Common Mistakes:

• Using 1D array for 2D interval data
• Incorrect brace nesting in initialization
• Swapping rows and columns in declaration

3. Given the following C code snippet, what is the output printed?

int intervals[3][2] = {{0, 30}, {5, 10}, {15, 20}};
// Assume a function minMeetingRooms(intervals, 3) returns minimum rooms needed
int rooms = minMeetingRooms(intervals, 3);
printf("%d\n", rooms);

Assuming minMeetingRooms correctly implements the meeting rooms logic, what is printed?

medium

A. 1

B. 3

C. 2

D. 0

Solution

1. Step 1: Analyze meeting intervals for overlaps

   Intervals: [0,30], [5,10], [15,20]. The first and second overlap (5 < 30), so need at least 2 rooms.

2. Step 2: Check if any three overlap simultaneously

   Third interval [15,20] overlaps with first [0,30], but second ends at 10, so max overlap is 2 meetings at once.

3. Final Answer:

   2 -> Option C

4. Quick Check:

   Max overlapping meetings = 2 [OK]

Hint: Count max overlaps to find rooms needed [OK]

Common Mistakes:

• Assuming all meetings overlap simultaneously
• Counting total meetings instead of overlaps
• Ignoring partial overlaps

4. The following C function aims to find the minimum number of meeting rooms required but has a bug. What is the bug?

int minMeetingRooms(int intervals[][2], int n) {
    int rooms = 0;
    for (int i = 0; i < n; i++) {
        for (int j = i + 1; j < n; j++) {
            if (intervals[i][0] < intervals[j][1] && intervals[j][0] < intervals[i][1]) {
                rooms++;
            }
        }
    }
    return rooms;
}

medium

A. It counts overlapping pairs but does not track maximum overlaps for rooms

B. It uses wrong indices in the loops causing out-of-bounds access

C. It returns zero always because rooms is never incremented

D. It sorts intervals incorrectly before counting overlaps

Solution

1. Step 1: Understand the nested loops and condition

   The code counts each overlapping pair by checking if intervals overlap and increments rooms.

2. Step 2: Identify why counting pairs is incorrect

   Counting pairs does not give the minimum rooms needed; we need the maximum number of simultaneous overlaps.

3. Final Answer:

   It counts overlapping pairs but does not track maximum overlaps for rooms -> Option A

4. Quick Check:

   Counting pairs ≠ max simultaneous overlaps [OK]

Hint: Track max overlaps, not just count pairs [OK]

Common Mistakes:

• Confusing pair counts with room count
• Not sorting intervals before processing
• Ignoring simultaneous overlaps

5. You have the following meeting intervals: [[1, 4], [2, 5], [7, 9], [3, 6], [10, 11]]. Using the minimum rooms required approach, what is the minimum number of meeting rooms needed?

hard

A. 2

B. 3

C. 4

D. 5

Solution

1. Step 1: Sort intervals by start time

   Sorted intervals: [1,4], [2,5], [3,6], [7,9], [10,11]

2. Step 2: Find maximum overlapping meetings

   Between 1-6, three meetings overlap: [1,4], [2,5], [3,6]. After 6, meetings do not overlap.

3. Final Answer:

   3 -> Option B

4. Quick Check:

   Max overlaps = 3 rooms needed [OK]

Hint: Sort intervals, count max overlaps for rooms [OK]

Common Mistakes:

• Not sorting intervals before counting
• Counting total meetings instead of overlaps
• Missing overlapping intervals in middle