55. Jump Game

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 <= 104
• 0 <= nums[i] <= 105

[想法]

Since we want to know if we can reach the last element, let’s set
goal = len(nums)-1

Next, let’s back forward to check if the previous element can reach the goal, nums[i] >= goal — i , if so, then update the goal to the previous element

Finally, check if the goal is equal to 0, if so, that means we are able to reach the last element

[Python Code]

def canJump(self, nums: List[int]) -> bool:
   goal = len(nums) - 1
   for i in range(len(nums)-1, -1, -1):
      if nums[i] >= goal - i:
         goal = i
   return True if goal==0 else False