Total Accepted: 87074 Total Submissions: 348588 Difficulty: Hard Contributors: Admin 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.
方法： 遍歷一遍，把正確合法的正整數方在正確的位置上即可。比如我們找到元素5，就把5換到A[4]上，因為數組從0下標開始。最終結果數組A[i] != i+1 的就是該位置上的正整數沒有出現過，返回i+1即可。
代碼如下：
class Solution(object): def firstMissingPositive(self, nums): n = len(nums) for i in range(0, n): while nums[i] > 0 and nums[i] <= n and nums[nums[i]-1] != nums[i]: nums[nums[i]-1], nums[i] = nums[i], nums[nums[i]-1] for i in range(0, n): if nums[i] != i+1: return i+1 return n+1呵呵，人生苦短，我用Python。
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