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 * 10^4
0 <= arr[i] < arr.length
0 <= start < arr.length
class Solution:
    def canReach(self, arr: List[int], start: int) -> bool:
        size = len(arr)
        visited = [0] * size
        def trackback(index):
            if arr[index] == 0:
                return True
            if index + arr[index] < size and visited[index+arr[index]] == 0:
                visited[index+arr[index]] = 1
                if trackback(index+arr[index]):
                    return True
            if index - arr[index] > -1 and visited[index-arr[index]] == 0:
                visited[index - arr[index]] = 1
                if trackback(index - arr[index]):
                    return True
            return False
        visited[start] = 1
        return trackback(start)
class Solution:
    def canReach(self, arr: List[int], start: int) -> bool:
        size = len(arr)
        visited = [0] * size
        def trackback(index):
            if arr[index] == 0:
                return True
            if index + arr[index] < size and visited[index+arr[index]] == 0:
                visited[index+arr[index]] = 1
                if trackback(index+arr[index]):
                    return True
            if index - arr[index] > -1 and visited[index-arr[index]] == 0:
                visited[index - arr[index]] = 1
                if trackback(index - arr[index]):
                    return True
            return False
        visited[start] = 1
        return trackback(start)