LeetCode 055 Jump Game

LeetCode

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 <= 10<sup>4</sup> 0 <= nums[i] <= 10<sup>5</sup>

题目大意：

N/A

解题思路：

BFS，但不需要用queue

解题步骤：

N/A

注意事项：

1. 参考Jump game II，区别在于如果i <= end才更新，
2. 返回next_end要大于等于(可以cover)最后一个元素下标

Python代码：

def canJump(self, nums: List[int]) -> bool:
	end, next_end = 0, 0
	for i in range(len(nums) - 1):
		if i <= end:
			next_end = max(next_end, i + nums[i]) # 4
		if i == end: #
			end = next_end # 8
	return next_end >= len(nums) - 1

算法分析：

时间复杂度为O(n)，空间复杂度O(1)