Leetcode-first Missing Positive

Topic:

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 .

Ideas:

The exchange is constant and the number of values I is exchanged to the position of (i-1) th.

 PackageArray; Public classfirstmissingpositive { Public intFirstmissingpositive (int[] nums) {        intN; if(Nums = =NULL|| (n = nums.length) = = 0)return1;  for(inti = 0; I < n; ++i) {intA =Nums[i];  while(A > 0 && a <= n && nums[i]! = i + 1 && nums[a-1]! =a) {swap (nums, I, a-1); A=Nums[i]; }        }                intj = 0;  while(J < n && nums[j] = = j + 1){            ++J; }        returnJ + 1; }        Private voidSwapint[] Nums,intIintj) {intTMP =Nums[i]; Nums[i]=Nums[j]; NUMS[J]=tmp; }         Public Static voidMain (string[] args) {//TODO auto-generated Method Stub        int[] Nums = { }; Firstmissingpositive F=Newfirstmissingpositive ();    System.out.println (F.firstmissingpositive (nums)); }}

Leetcode-first Missing Positive