Jump Game Problem in DSA Go - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start iterating over the jump array.

DSA Go

for [1] := 0; [1] < len(nums); [1]++ {

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

Ai

Bj

Cindex

Dpos

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable not declared in the loop header.

The loop variable should be 'i' to iterate over the array indices.

2fill in blank

medium

Complete the code to update the furthest reachable index.

DSA Go

if i + nums[i] > [1] {
    maxReach = i + nums[i]
}

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Areach

Bfurthest

CmaxIndex

DmaxReach

Attempts:

3 left

💡 Hint

Common Mistakes

Using an undefined variable name.

We compare with 'maxReach' to update the furthest reachable index.

3fill in blank

hard

Fix the error in the condition to check if the current index is reachable.

DSA Go

if i > [1] {
    return false
}

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Alen(nums)

Bi

CmaxReach

Dnums[i]

Attempts:

3 left

💡 Hint

Common Mistakes

Comparing 'i' with itself or array length incorrectly.

If current index 'i' is beyond 'maxReach', it means we cannot reach it.

4fill in blank

hard

Fill both blanks to complete the function signature and return type.

DSA Go

func canJump(nums []int) [1] {
    maxReach := 0
    for i := 0; i < len(nums); i++ {
        if i > maxReach {
            return [2]
        }
        if i + nums[i] > maxReach {
            maxReach = i + nums[i]
        }
    }
    return true
}

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

Abool

Bint

Cfalse

Dtrue

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong return type or returning true too early.

The function returns a boolean, and returns false if the current index is unreachable.

5fill in blank

hard

Fill all three blanks to complete the main function that tests canJump.

DSA Go

func main() {
    nums := []int[1]
    result := canJump(nums)
    if result == [2] {
        fmt.Println("Can reach the end")
    } else {
        fmt.Println("Cannot reach the end")
    }
}

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

A{2,3,1,1,4}

Btrue

Cfalse

D{3,2,1,0,4}

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong slice syntax or wrong boolean values.

The array {2,3,1,1,4} allows reaching the end, so result is true; {3,2,1,0,4} is an example input.

Practice

1. What does the Jump Game problem ask you to determine given an array of non-negative integers?

easy

A. If you can reach the last index starting from the first index by jumping within allowed steps

B. The maximum jump length you can make from any position

C. The minimum number of jumps to reach the last index

D. The sum of all jump lengths in the array

Solution

1. Step 1: Understand the problem statement

   The Jump Game problem asks if you can move from the first index to the last index by jumping forward within the allowed steps at each position.

2. Step 2: Identify the key question

   The key question is whether the last index is reachable, not how many jumps or maximum jump length.

3. Final Answer:

   If you can reach the last index starting from the first index by jumping within allowed steps -> Option A

4. Quick Check:

   Jump Game = Reach last index? [OK]

Hint: Focus on reachability, not jump count or max jump length [OK]

Common Mistakes:

• Confusing reachability with minimum jumps
• Thinking about maximum jump length instead
• Assuming sum of jumps matters

2. Which of the following Go code snippets correctly declares an integer slice representing jump lengths for the Jump Game?

easy

A. jumps := [2, 3, 1, 1, 4]

B. jumps := (2, 3, 1, 1, 4)

C. jumps := int{2, 3, 1, 1, 4}

D. jumps := []int{2, 3, 1, 1, 4}

Solution

1. Step 1: Recall Go slice declaration syntax

   In Go, slices are declared with []type and curly braces for values, e.g., []int{...}.

2. Step 2: Check each option

   Only jumps := []int{2, 3, 1, 1, 4} uses correct slice syntax. The others use array syntax, invalid int{}, or parentheses.

3. Final Answer:

   jumps := []int{2, 3, 1, 1, 4} -> Option D

4. Quick Check:

   Slice declaration = []int{values} [OK]

Hint: Use []int{...} to declare integer slices in Go [OK]

Common Mistakes:

• Using square brackets without type for slices
• Using parentheses instead of braces
• Confusing arrays and slices syntax

3. What is the output of the following Go code snippet for the Jump Game problem?

package main

import "fmt"

func canJump(nums []int) bool {
    maxReach := 0
    for i := 0; i < len(nums); i++ {
        if i > maxReach {
            return false
        }
        if i+nums[i] > maxReach {
            maxReach = i + nums[i]
        }
    }
    return true
}

func main() {
    nums := []int{2, 3, 1, 1, 4}
    fmt.Println(canJump(nums))
}

medium

A. true

B. false

C. Compilation error

D. Runtime panic

Solution

1. Step 1: Trace maxReach updates

   Start maxReach=0. At i=0, maxReach=max(0,0+2)=2. i=1 ≤ 2, maxReach=max(2,1+3)=4. i=2 ≤ 4, maxReach=max(4,2+1)=4. i=3 ≤ 4, maxReach=max(4,3+1)=4. i=4 ≤ 4, maxReach=max(4,4+4)=8.

2. Step 2: Check if any index is unreachable

   All i ≤ maxReach, so no false return. Loop ends, returns true.

3. Final Answer:

   true -> Option A

4. Quick Check:

   All indices reachable = true [OK]

Hint: Track max reachable index; if current index exceeds it, return false [OK]

Common Mistakes:

• Not updating maxReach correctly
• Returning false too early
• Ignoring the condition i > maxReach

4. Identify the bug in this Go function for the Jump Game problem and select the fix:

func canJump(nums []int) bool {
    maxReach := 0
    for i := 0; i <= len(nums); i++ {
        if i > maxReach {
            return false
        }
        if i+nums[i] > maxReach {
            maxReach = i + nums[i]
        }
    }
    return true
}

medium

A. Remove the if condition checking i > maxReach

B. Initialize maxReach to 1 instead of 0

C. Change loop condition to i < len(nums)

D. Change return false to return true inside the loop

Solution

1. Step 1: Analyze loop boundary

   The loop runs with i <= len(nums), which causes index out of range error at i == len(nums).

2. Step 2: Fix loop condition

   Changing to i < len(nums) prevents out of range access and fixes the bug.

3. Final Answer:

   Change loop condition to i < len(nums) -> Option C

4. Quick Check:

   Loop index must be less than slice length [OK]

Hint: Use i < len(slice) to avoid index out of range errors [OK]

Common Mistakes:

• Using <= instead of < in loop condition
• Ignoring runtime panic from out of range
• Changing unrelated parts of code

5. Given the array nums := []int{3, 2, 1, 0, 4}, what is the result of applying the Jump Game algorithm to check if the last index is reachable?

hard

A. true

B. false

C. Runtime error due to zero jump

D. Depends on starting index

Solution

1. Step 1: Trace maxReach through the array

   Start maxReach=0. i=0: maxReach=max(0,0+3)=3. i=1 ≤ 3: maxReach=max(3,1+2)=3. i=2 ≤ 3: maxReach=max(3,2+1)=3. i=3 ≤ 3: maxReach=max(3,3+0)=3. i=4 > 3, so return false.

2. Step 2: Understand why last index is unreachable

   At index 3, jump length is 0, so maxReach does not increase. Index 4 is beyond maxReach, unreachable.

3. Final Answer:

   false -> Option B

4. Quick Check:

   Zero jump blocks progress = false [OK]

Hint: If maxReach stops before last index, return false [OK]

Common Mistakes:

• Assuming zero jump can be bypassed
• Ignoring unreachable last index
• Thinking runtime error occurs