[LeetCode] First Missing Positive

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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.

在原數組A上將數組A中的數進行排序....時間複雜度O(n),空間複雜度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