[Leetcode] 228. Summary Ranges (Easy)

概述

題目

https://leetcode.com/problems/summary-ranges/
給出至多 20 個數，求其區間結果為何

心得

本題較為細碎，但實際小心判斷完即可 AC

Two Pointer

思路

前一指針 pre 表示上一次連續到現在的結果，後指針 go through 所有數字

程式

class Solution(object):
    def summaryRanges(self, nums):
        """
        :type nums: List[int]
        :rtype: List[str]
        """
        # 長度為 0 或 1 之特例
        if len(nums) == 0:
            return []
        elif len(nums) == 1:
            return [str(nums[0])]
            
        ret = []
        pre = -1
        for c in nums:
            if c+1 not in nums:
                if pre == -1:
                    ret.append(str(c))
                else:
                    ret.append(str(pre)+"->"+str(c))
                    pre = -1
            else:
                if pre == -1:
                    pre = c

        if pre == nums[-1]:
            ret.append(str(c))
        elif pre != -1:
            ret.append(str(pre)+"->"+str(nums[-1]))
        return ret

from StefanPochmann 大神

class Solution(object):
   def summaryRanges(self, nums):
       """
       :type nums: List[int]
       :rtype: List[str]
       """
       arr = []
       
       for c in nums:
           if not arr or c > arr[-1][-1] + 1:
               arr.append([])
               # arr += [],
           arr[-1][1:] = [c]
           # arr[-1][1:] = c,
       return ["->".join(map(str, c)) for c in arr]