[leetcode] 55. Jump Game @ python

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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