Aggressive Cows Maximum Minimum Distance in DSA Go - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to sort the stall positions.

DSA Go

sort.[1](stalls)

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

AInts

BSlice

CFloat64s

DStrings

Attempts:

3 left

💡 Hint

Common Mistakes

Using sort.Strings on integer slice causes compile error.

Trying to sort without importing sort package.

We use sort.Ints to sort a slice of integers representing stall positions.

2fill in blank

medium

Complete the code to check if cows can be placed with given minimum distance.

DSA Go

if stalls[i]-lastPos >= [1] {

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

AmidDist

BminDist

CmaxDist

Ddistance

Attempts:

3 left

💡 Hint

Common Mistakes

Using maxDist instead of minDist causes wrong logic.

Comparing with midDist which is not defined here.

We check if the distance between current stall and last placed cow is at least minDist.

3fill in blank

hard

Fix the error in the binary search loop condition.

DSA Go

for low <= [1] {

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

Ahigh

Bmid

Clow

DmaxDist

Attempts:

3 left

💡 Hint

Common Mistakes

Using low < mid causes infinite loop.

Using high < low reverses the condition.

The binary search continues while low is less than or equal to high.

4fill in blank

hard

Fill both blanks to update the binary search bounds correctly.

DSA Go

if canPlaceCows(stalls, cows, [1]) {
    result = [2]
    low = mid + 1
} else {
    high = mid - 1
}

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

Amid

Blow

Dhigh

Attempts:

3 left

💡 Hint

Common Mistakes

Updating result to low or high instead of mid.

Incorrectly updating low or high bounds.

If cows can be placed at distance mid, update result to mid and search higher by setting low = mid + 1.

5fill in blank

hard

Fill all three blanks to complete the canPlaceCows function logic.

DSA Go

count := 1
lastPos := stalls[0]
for i := 1; i < len(stalls); i++ {
    if stalls[i]-lastPos >= [1] {
        count++
        lastPos = stalls[i]
        if count == [2] {
            return [3]
        }
    }
}
return false

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

AminDist

Bcows

Ctrue

Dfalse

Attempts:

3 left

💡 Hint

Common Mistakes

Returning false instead of true when all cows placed.

Using wrong variable names for count or distance.

We place cows if distance is at least minDist, count cows placed, and return true if all cows are placed.

Practice

1. What is the main goal of the Aggressive Cows Maximum Minimum Distance problem?

easy

A. To arrange cows in increasing order of their stall numbers

B. To find the maximum number of cows that can fit in a single stall

C. To minimize the distance between all cows placed in the stalls

D. To place cows in stalls so that the minimum distance between any two cows is as large as possible

Solution

1. Step 1: Understand the problem objective

   The problem asks to place cows in given stalls such that the smallest distance between any two cows is as large as possible.

2. Step 2: Clarify the goal

   This means maximizing the minimum distance between cows, not minimizing or counting cows in one stall.

3. Final Answer:

   To place cows in stalls so that the minimum distance between any two cows is as large as possible -> Option D

4. Quick Check:

   Maximize minimum distance = Place cows far apart [OK]

Hint: Focus on maximizing the smallest gap between cows [OK]

Common Mistakes:

• Thinking the goal is to minimize distance
• Confusing number of cows with distance
• Assuming cows can share stalls

2. Which of the following Go function signatures correctly represents the binary search helper function used in the Aggressive Cows problem?

easy

A. func canPlaceCows(stalls []int, dist int) bool

B. func canPlaceCows(cows int, dist int, stalls []int) int

C. func canPlaceCows(stalls []int, cows int, dist int) bool

D. func canPlaceCows(stalls []int, cows int) int

Solution

1. Step 1: Identify required parameters

   The helper function needs stalls array, number of cows, and distance to check feasibility.

2. Step 2: Match correct signature

   func canPlaceCows(stalls []int, cows int, dist int) bool has all parameters in correct order and returns bool indicating if placement is possible.

3. Final Answer:

   func canPlaceCows(stalls []int, cows int, dist int) bool -> Option C

4. Quick Check:

   Parameters: stalls, cows, dist; returns bool [OK]

Hint: Helper checks feasibility, needs stalls, cows, distance [OK]

Common Mistakes:

• Wrong parameter order
• Missing cows or distance parameter
• Returning int instead of bool

3. Given stalls at positions [1, 2, 8, 4, 9] and 3 cows, what is the maximum minimum distance between any two cows after running the Aggressive Cows algorithm?

medium

A. 3

B. 4

C. 5

D. 2

Solution

1. Step 1: Sort stalls and set search range

   Sorted stalls: [1, 2, 4, 8, 9]. Minimum distance = 1, maximum = 8 (9-1).

2. Step 2: Binary search for max minimum distance

   Check mid=4: place first at 1 (last=1), skip 2 (1<4), skip 4 (3<4), place 8 (7>=4, count=2, last=8), skip 9 (1<4). Only 2 cows, fail.

3. Step 3: Check mid=3

   Place first at 1 (last=1), skip 2 (1<3), place 4 (3>=3, count=2, last=4), place 8 (4>=3, count=3, last=8), skip 9 (1<3). 3 cows placed, success.

4. Step 4: Final answer

   Maximum minimum distance is 3 (e.g., 1,4,8).

5. Final Answer:

   3 -> Option A

6. Quick Check:

   Max min distance = 3 [OK]

Hint: Sort stalls, binary search distance, check feasibility [OK]

Common Mistakes:

• Not sorting stalls before processing
• Incorrect binary search mid calculation
• Miscounting cows placed at given distance

4. Consider this Go snippet for checking if cows can be placed:

func canPlaceCows(stalls []int, cows int, dist int) bool {
    count := 1
    lastPos := stalls[0]
    for i := 1; i < len(stalls); i++ {
        if stalls[i]-lastPos >= dist {
            count++
            lastPos = stalls[i]
        }
    }
    return count >= cows
}

What is the bug if stalls array is not sorted before calling this function?

medium

A. The function may incorrectly count placements because stalls are unordered

B. The function will cause a runtime panic due to index out of range

C. The function will always return false

D. No bug; sorting is not required

Solution

1. Step 1: Understand function logic

   The function assumes stalls are sorted to place cows greedily at increasing positions.

2. Step 2: Effect of unsorted stalls

   If stalls are unordered, distance checks become invalid, causing wrong count of cows placed.

3. Final Answer:

   The function may incorrectly count placements because stalls are unordered -> Option A

4. Quick Check:

   Unsorted stalls break greedy placement logic [OK]

Hint: Always sort stalls before placement check [OK]

Common Mistakes:

• Ignoring sorting requirement
• Assuming function panics without sorting
• Thinking function always fails without sorting

5. You have stalls at positions [5, 10, 15, 20, 25, 30] and need to place 4 cows. If the minimum distance between cows must be at least 7, which is the correct maximum minimum distance achievable?

hard

A. 7

B. 5

C. 15

D. 10

Solution

1. Step 1: Analyze stall positions

   Stalls: [5,10,15,20,25,30] (spaced by 5), 4 cows.

2. Step 2: Check dist=10

   Greedy: place at 5 (last=5), skip 10 (5<10), place 15 (10>=10), skip 20 (5<10), place 25 (10>=10), skip 30 (5<10). 3 cows placed, fail.

3. Step 3: Check dist=7

   Greedy: place at 5 (last=5), skip 10 (5<7), place 15 (10>=7), skip 20 (5<7), place 25 (10>=7), place 30 (5>=7? No, 5<7), so only 3 cows placed, fail.

4. Step 4: Check dist=6

   Similar to above, 3 cows placed, fail.

5. Step 5: Check dist=5

   Greedy: place at 5, 10, 15, 20 (all distances >=5), 4 cows placed, success.

6. Step 6: Final answer

   Maximum minimum distance is 5, since 7 or more fails to place 4 cows.

7. Final Answer:

   5 -> Option B

8. Quick Check:

   Max min distance = 5 [OK]

Hint: Test distances with binary search and feasibility check [OK]

Common Mistakes:

• Assuming max distance is stall range without checks
• Ignoring minimum distance constraint
• Misplacing cows ignoring stall positions