1306. Jump Game III

Medium

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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

class Solution:
    def __init__(self):
        self.visited = set()
    def canReach(self, arr: List[int], start: int) -> bool:
        if start < 0 or start >= len(arr):
            return False
        # print(start)
        self.visited.add(start)
        if arr[start] == 0:
            return True
        left = False
        right = False
        if (start-arr[start]) not in self.visited:
            left = self.canReach(arr, start - arr[start])
        if (start + arr[start]) not in self.visited:
            right = self.canReach(arr, start + arr[start])
        return left or right