[leetcode] 55. Jump Game @ python

跳过数组的贪心算法

最新推荐文章于 2020-05-10 15:39:09 发布

原创最新推荐文章于 2020-05-10 15:39:09 发布 · 440 阅读

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探讨了如何使用贪心算法解决能否从数组起始位置跳跃到末尾的问题。通过维护一个变量far来记录当前能到达的最大下标，遍历数组并更新far，判断是否能到达最后一个元素。

原题

Given an array of non-negative integers, you are initially positioned at the first index of the array.

Each element in the array represents your maximum jump length at that position.

Determine if you are able to reach the last index.

Example 1:

Input: [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: [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.

解法

贪心算法, 用far来表示当前能到达的最大index, 初始化far = nums[0]. 遍历nums, 更新far

far = max(far, i + nums[i])

如果走到i 点发现 i > far, 表现i 点无法到达, 返回False, 遍历完成之后检查far >= len(nums) -1

代码

class Solution(object):
    def canJump(self, nums):
        """
        :type nums: List[int]
        :rtype: bool
        """
        # far means the farthest index you can jump to
        far = nums[0]
        for i in range(len(nums)):
            if i > far:
                # it means we cannot reach i, break
                return False
            far = max(far, i + nums[i])
        return far >= len(nums)-1