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