MUX MUX - Vaibhav

#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;

int firstMissingNonNegative(vector<int>& nums) {
        int n=nums.size();
        for(int i=0;i<n;i++){
            if(nums[i]>=0 && nums[i]<n && nums[i]!=nums[nums[i]]){
                swap(nums[i],nums[nums[i]]);
                i--;
            }
        }

        for(int i=0;i<n;i++){
            if(nums[i]!=i)
                return i;
        }

        return n;
}

int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */
    int t;
    cin>>t;

    while(t--){
        int n;
        cin>>n;
        vector<int> nums;

        for(int i = 0; i<n; i++){
            int val;
            cin>>val;
            nums.push_back(val);
        }

        int ans = firstMissingNonNegative(nums);

        cout<<ans<<endl;
    }
}