Leetcode: Missing Number

Given an array containing n distinct numbers taken from 0, 1, 2, ..., n, find the one that is missing from the array.

For example,
Given nums = [0, 1, 3] return 2.

Note:
Your algorithm should run in linear runtime complexity. Could you implement it using only constant extra space complexity?

 1 public class Solution {
 2     public int missingNumber(int[] nums) {
 3         int res = nums.length;
 4         for (int i=0; i<nums.length; i++) {
 5             if (nums[i] < nums.length && nums[i] != i) {
 6                 int temp = nums[nums[i]];
 7                 nums[nums[i]] = nums[i];
 8                 nums[i] = temp;
 9                 i--;
10             }
11         }
12         for (int i=0; i<nums.length; i++) {
13             if (nums[i] != i) res = i;
14         }
15         return res;
16     }
17 }