20170611-leetcode-041-First Missing Positive

1.Description

Given an unsorted integer array, find the first missing positive integer.

For example,

Given

[1,2,0]

return

3

,

and

[3,4,-1,1]

return

2

.

Your algorithm should run in O(n) time and uses constant space.

解读

给定一个无序的数组，找到第一个缺失的正整数,要求时间为 O ( n )

比如：【1,2,0】，返回3

【900，-1】，返回1

2.Solution

思路：找到最大值，然后遍历一下

class Solution(object):
def firstMissingPositive(self, nums):
if not nums: return 1
maxNum = max(nums)
for i in range(1, maxNum + 2):
if i not in nums:
return i