45. Jump Game II
原理来挺简单的，就是把每一步可以达到的最远距离计算出来，有点像dynamic window的题目，只是left boundary是固定的 lastend + 1，right boundary是上一步能跳到的最大长度，不停的更新就可以了。

class Solution(object):
    def jump(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        # get maximum jump in each jump
        if not nums or len(nums) == 1:
            return 0
        start = 0
        end = start + nums[0]
        count = 1
        while end < len(nums)-1:
            new_end = end
            for i in range(start, end+1):
                new_end = max(new_end, i + nums[i])
            
            start = end + 1
            end = new_end
            count += 1
        
        return count