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.
在原数组A上将数组A中的数进行排序....时间复杂度O(n),空间复杂度O(1)
class Solution { public: int firstMissingPositive(int A[], int n) { if(n==0) return 1; for(int i=0;i<n;i++){ if(A[i] <= n && A[i]>0 && A[i] != i+1){ if(A[A[i]-1] != A[i]){ int tmp = A[A[i]-1]; A[A[i]-1] = A[i]; A[i] = tmp; i--; } } }//end for for(int i=0;i<n;i++){ if(A[i] != i+1) return i+1; } return n+1; } };
[LeetCode] First Missing Positive
原文：http://www.cnblogs.com/Xylophone/p/3933351.html