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1306. Jump Game III

Difficulty Topics

Description

Given an array of non-negative integers arr, you are initially positioned at start index of the array. When you are at index i, you can jump to i + arr[i] or i - arr[i], check if you can reach to any index with value 0.

Notice that you can not jump outside of the array at any time.

 

Example 1:

Input: arr = [4,2,3,0,3,1,2], start = 5
Output: true
Explanation: 
All possible ways to reach at index 3 with value 0 are: 
index 5 -> index 4 -> index 1 -> index 3 
index 5 -> index 6 -> index 4 -> index 1 -> index 3

Example 2:

Input: arr = [4,2,3,0,3,1,2], start = 0
Output: true 
Explanation: 
One possible way to reach at index 3 with value 0 is: 
index 0 -> index 4 -> index 1 -> index 3

Example 3:

Input: arr = [3,0,2,1,2], start = 2
Output: false
Explanation: There is no way to reach at index 1 with value 0.

 

Constraints:

  • 1 <= arr.length <= 5 * 104
  • 0 <= arr[i] < arr.length
  • 0 <= start < arr.length

Solution

jump-game-iii.py
class Solution:
    def canReach(self, arr: List[int], start: int) -> bool:
        n = len(arr)
        queue = deque([start])
        visited = [False] * n
        visited[start] = True

        while queue:
            index = queue.popleft()

            if arr[index] == 0: return True

            for j in [(index + arr[index]), (index - arr[index])]:
                if 0 <= j < n and not visited[j]:
                    visited[j] = True
                    queue.append(j)

        return False