def firstMissingPositive(nums):
    """
    :type nums: List[int]
    :rtype: int
    """
    if not nums:
        return 1
    for i,v in enumerate(nums):
        if v > len(nums):
            nums[i]=-1
        elif v <= 0:
            nums[i]=-1
        else:
            while i+1 != nums[i] and 0<nums[i]<=len(nums):
                #print i, nums[i]-1, nums[i], nums[nums[i]-1]
                v = nums[i]
                nums[i] = nums[v-1]
                nums[v-1] = v
                #nums[i], nums[nums[i]-1] = nums[nums[i]-1], nums[i]
            if nums[i] > len(nums) or nums[i] <=0:
                nums[i] = -1
    for i,v in enumerate(nums):
        if nums[i] != i+1:
            return i+1
    return len(nums)+1

if __name__ == "__main__":
    print firstMissingPositive([1,2,0])
    print firstMissingPositive([3,4,-1,1])

for i,v in enumerate(nums)

for i,v in enumerate(nums):
    if v > len(nums):
        nums[i]=-1
    elif v <= 0:
        nums[i]=-1
    else:

if  0 >= value > len(nums):
    continue

def first_missing_positive(nums):
    """
    :type nums: List[int]
    :rtype: int
    """
    if not nums:
        return 1
    for index, value in enumerate(nums):
        if len(nums) < value <= 0:
            continue
        while index + 1 != nums[index] and 0 < nums[index] <= len(nums):
            v = nums[index]
            nums[index], nums[v-1] = nums[v-1], nums[index]
            nums[v-1] = v

            # Don't create infinite loops
            if nums[index] == nums[v-1]:
                break

    for index, value in enumerate(nums, 1):
        if value != index:
            return index
    return len(nums) + 1

def first_missing_positive(nums):
    cnt = {}
    for x in nums:
        cnt[x] = 1

    fnd = 1
    for i in range(len(nums)):
        if cnt.get(fnd, 0) == 0:
            return fnd
        fnd += 1
    return fnd