First Missing Integer Asked in: Model N InMobi Amazon

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

Example:

Given [1,2,0] return 3,

[3,4,-1,1] return 2,

[-8, -7, -6] returns 1

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

Solution:

class Solution:

# @param A : list of integers

# @return an integer

def firstMissingPositive(self, A):

A=set(A)

i=1

while(1):

if i not in A:

return i

i+=1

return i+1

Solution ScreenShot:

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