LeetCode-in-All
55. Jump Game
Medium
You are given an integer array nums. You are initially positioned at the array’s first index, and each element in the array represents your maximum jump length at that position.
Return true if you can reach the last index, or false otherwise.
Example 1:
Input: nums = [2,3,1,1,4]
Output: true
Explanation: Jump 1 step from index 0 to 1, then 3 steps to the last index.
Example 2:
Input: nums = [3,2,1,0,4]
Output: false
Explanation: You will always arrive at index 3 no matter what. Its maximum jump length is 0, which makes it impossible to reach the last index.
Constraints:
1 <= nums.length <= 1040 <= nums[i] <= 105
Solution
defmodule Solution do
@spec can_jump(nums :: [integer]) :: boolean
def can_jump(nums) do
can?(0, length(nums) - 1, nums)
end
defp can?(reach, dist, _) when reach >= dist, do: true
defp can?(reach, _, _) when reach < 0, do: false
defp can?(reach, dist, [head | tail]) do
can?(max(reach, head) - 1, dist - 1, tail)
end
end