题目
Given an array containing n distinct numbers taken from 0, 1, 2, …, n, find the one that is missing from the array.
Example 1
Input: [3,0,1]
Output: 2
Example 2
Input: [9,6,4,2,3,5,7,0,1]
Output: 8
Note:
Your algorithm should run in linear runtime complexity. Could you implement it using only constant extra space complexity?
题意
这道题是说给出一个长度为N的数组,数组内容是从0-N的不同数字,找出那个缺失的(N+1 - N)的数字
想法
感觉这道题很有意思,乍一看,要求只有线性运算时间,又只用一个常量的辅助空间,貌似很难,但是仔细一想,有种会心的感觉,这不就是你目标序列已知了:(1)递增序列,从0开始到N,目标和已知;(2)互异,值唯一;
最后的解法就是先求目标和和实际和,相减得到那个唯一缺失值。
参考代码
class Solution(object):
def missingNumber(self, nums):
"""
:type nums: List[int]
:rtype: int
"""
return (0+len(nums))*(1+len(nums))/2 - sum(nums)