55. Jump Game/45. Jump Game II

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1. 55. Jump Game
   思路：[greedy] 得到所能走到的最大距离，与最终结果比较

class Solution:
    def canJump(self, nums):
        """
        :type nums: List[int]
        :rtype: bool
        """
        max_nums=nums[0]
        x=0
        while x<min(max_nums+1,len(nums)):
            if nums[x]+x>max_nums:max_nums=nums[x]+x
            x+=1
        return max_nums>=len(nums)-1
 

下面的思路更清晰

class Solution:
    def canJump(self, nums):
        """
        :type nums: List[int]
        :rtype: bool
        """
        #greedy reach最远可达的位置
        reach = 0
        for i in range(len(nums)):
            #reach = max(reach, i+nums[i])
            if i > reach or reach >= len(nums)-1:
                break
            reach = max(reach, i+nums[i])
        return reach >= len(nums)-1

2. 45. Jump Game II
   思路：算出第一步最远距离，第二步最远距离，直到符合要求，

# 45. Jump Game II
# 
class Solution:
    def jump(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        if len(nums)==1:return 0

        # 步数
        steps=1
        # 每一步所能到达的最远
        max_reach=nums[0]
        # 每一个位置所能到达最远
        step_reach=nums[0]

        x=0
        while x<len(nums):
            # 切换步数条件
            if max_reach<x:
                steps+=1
                max_reach=step_reach
            step_reach=max(step_reach,x+nums[x])

            x+=1
            
            if max_reach>len(nums)-2:return steps