Leetcode:first Missing Positive

Title:

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.

Idea: Put the element in the appropriate position, for example 1 placed in the array 0 position, 2 put to 1 position ...

intFirstmissingpositive (intA[],intN) { for(inti =0; I < n; i++){             while(A[i]! = i+1){                if(A[i] >= n | | A[i] <=0|| A[i] = = a[a[i-1]])//A[i] = = A[a[i]-1] It is judged that if the two elements themselves are equal, they do not have to be exchanged, or they will fall into a dead loop .                     Break; //Exchange A[i] and A[a[i]-1]                intt =A[i]; A[i]= a[t-1]; A[t-1] =T; }        } for(inti =0; I < n; i++){            if(A[i]! = i+1)                returni+1; }        returnn+1; }

Leetcode:first Missing Positive