268. Missing Number

public class Solution {
    public int missingNumber(int[] nums) {
        int size=nums.length;
        
        int res[]=new int[size+1];
        
        for(int i=0;i<=size;i++)
        {
            res[i]=0;
        }
        for(int i=0;i<size;i++)
        {
            res[nums[i]]=1;
        }
        
        int answer=0;
        for(int i=0;i<=size;i++)
        {
            if(res[i]==0)
            {
                answer=i;
                break;
            }
        }
        
        return answer;
    }
}