DSA Visualizations | Hello Interview

Jump Game

DESCRIPTION (credit Leetcode.com)

Write a function to determine whether you can travel from the first index to the last index of an integer array nums, where each number in the array specifies the maximum distance you can jump from that index. The function should return true if reaching the last index is possible, and false otherwise.

EXAMPLES

Input:


nums = [1, 3, 0, 1, 4]

Output:


true

Explanation: You can jump from index 0 to index 1, then jump from index 1 to index 4 which is the last index.

Example: Input:


nums = [2,2,1,0,5,1,1]

Output:


false

Explanation: The first three indexes take you to index 3 no matter what. But you cannot move beyond index 3 because its maximum jump length is 0, making the indexes after index 3 unreachable.

Solution


def canJump(nums):
  max_reach = 0
  for i in range(len(nums)):
    if i > max_reach:
      return False
    max_reach = max(max_reach, i + nums[i])
  return True

jump game

0 / 12

Explanation

We can solve this problem using a greedy approach. We'll iterate through the array, and greedily see how far we can reach if we were to jump from that index. We'll use a variable max_reach that stores the maximum index we can reach using the indexes we have visited so far.

If at any point, the current index is greater than max_reach, then we return false because we would never be able to reach that index from the previous indexes, which thus makes it impossible to reach the end of the array.

Otherwise, we update max_reach to be the maximum of max_reach and i + nums[i] (representing the maximum index we can reach from the current index), and continue iterating through the array. If we reach the end of the array, then we return true.

Returning False

Here's an example of an input array that would return false. We can reach index 3, but since the maximum jump length at index 3 is 0, we can't reach anything beyond that.


def canJump(nums):
  max_reach = 0
  for i in range(len(nums)):
    if i > max_reach:
      return False
    max_reach = max(max_reach, i + nums[i])
  return True

jump game

0 / 11

Time Complexity

Time Complexity: O(n) where n is the length of the input array nums.
Space Complexity: O(1) since we are using a constant amount of space.

Next: Overview

Your account is free and you can post anonymously if you choose.

Sort By

Loading comments...

Back to Home

Eliminating Pairs

Overview

Container With Most Water

3-Sum

Triangle Numbers

Pointers as Regions

Move Zeroes

Sort Colors

Trapping Rain Water

Variable-Length

Overview

Longest Substring Without Repeating Characters

Longest Repeating Character Replacement

Fixed-Length

Overview

Maximum Sum of Subarrays of Size K

Max Points You Can Obtain From Cards

Max Sum of Distinct Subarrays Length k

Overview

Can Attend Meetings

Insert Interval

Non-Overlapping Intervals

Merge Intervals

Employee Free Time

Overview

Valid Parentheses

Decode String

Longest Valid Parentheses

Monotonic Stack

Overview

Daily Temperatures

Largest Rectangle in Histogram

Overview

Linked List Cycle

Palindrome Linked List

Remove Nth Node From End of List

Reorder List

Swap Nodes in Pairs

Overview

Apple Harvest (Koko Eating Bananas)

Search in Rotated Sorted Array

Overview

Kth Largest Element in an Array

K Closest Points to Origin

Find K Closest Elements

Merge K Sorted Lists

Introduction

Binary Trees

Overview

Level Order Sum

Rightmost Node

Zigzag Level Order

Maximum Width of Binary Tree

Graphs

Overview

Minimum Knight Moves

Rotting Oranges

01-Matrix

Bus Routes

Overview

Word Search

Solution Space Trees

Subsets

Generate Parentheses

Combination Sum

Topological Sort

Overview

Course Schedule

Course Schedule II

Fundamentals

Solving a Question with Dynamic Programming

Counting Bits

Decode Ways

Maximal Square

Unique Paths

Longest Increasing Subsequence

Word Break

Maximum Profit in Job Scheduling

Overview

Best Time to Buy and Sell Stock

Gas Station

Jump Game

Overview

Implement Trie Methods

Prefix Matching

Overview

Count Vowels in Substrings

Subarray Sum Equals K

Spiral Matrix

Rotate Image

Set Matrix Zeroes

Gas Station

Trie: Overview

Jump Game

DESCRIPTION (credit Leetcode.com)

EXAMPLES

Input:


nums = [1, 3, 0, 1, 4]

Output:


true

Explanation: You can jump from index 0 to index 1, then jump from index 1 to index 4 which is the last index.

Example: Input:


nums = [2,2,1,0,5,1,1]

Output:


false

Explanation: The first three indexes take you to index 3 no matter what. But you cannot move beyond index 3 because its maximum jump length is 0, making the indexes after index 3 unreachable.

Solution


def canJump(nums):
  max_reach = 0
  for i in range(len(nums)):
    if i > max_reach:
      return False
    max_reach = max(max_reach, i + nums[i])
  return True

jump game

0 / 12

Explanation

Returning False

Here's an example of an input array that would return false. We can reach index 3, but since the maximum jump length at index 3 is 0, we can't reach anything beyond that.


def canJump(nums):
  max_reach = 0
  for i in range(len(nums)):
    if i > max_reach:
      return False
    max_reach = max(max_reach, i + nums[i])
  return True

jump game

0 / 11

Time Complexity

Time Complexity: O(n) where n is the length of the input array nums.
Space Complexity: O(1) since we are using a constant amount of space.

Next: Overview

Your account is free and you can post anonymously if you choose.

Sort By

Loading comments...

BlogBehavioral Interview Examples Interviewing for Experienced SWEs All Blog Posts

Compare UsCompare to Interviewing.io

LinksFAQ Schedule Mock Interviews Pricing Become a Coach Our Coaches Learn System Design Learn DSA Guided Practice Hello Interview Premium

LegalTerms and Conditions Privacy Policy

Contactsupport@hellointerview.com7511 Greenwood Ave North
Unit #4238 Seattle, WA 98103