1306. Jump Game III

Medium

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

解題

DFS

Runtime: 68 ms, faster than 75.44%

Memory Usage: 11.1 MB, less than 36.84%

func canReach(arr []int, start int) bool {
    record := make([]bool, len(arr))

    var jump func(int) bool
    jump = func(index int) bool {
        if index < 0 || index >= len(arr) {
            return false
        }

        if record[index] {
            return false
        }

        if arr[index] == 0 {
            return true
        }

        record[index] = true
        return jump(index + arr[index]) || jump(index - arr[index])
    }

    return jump(start)
}