Swap two nibbles

#include<bits/stdc++.h>
using namespace std;

vector<int> dec_to_binary(int x){
    vector<int> binary;
    int count = 8;
    while(count--){
        int k = x % 2;
        binary.push_back(k);
        x /= 2;
    }
    return binary;
}

vector<int> change(vector<int> &binary){
    swap(binary[0], binary[4]);
    swap(binary[1], binary[5]);
    swap(binary[2], binary[6]);
    swap(binary[3], binary[7]);
}

void show_binary(vector<int> binary){
    for(int i = binary.size()-1; i > -1; i--){
        cout << binary[i];
    }
    cout << endl;
}

int binary_to_decimal(vector<int> binary){
    int base = 1, decimal = 0;
    for(int i = 0; i < binary.size(); i++){
        int k = binary[i] * base;
        decimal += k;
        base *= 2;
    }
    return decimal;
}

int main(){
    int t; cin >> t;
    while(t--){
        int x; cin >> x;
        vector<int> binary = dec_to_binary(x);

        //  Showing the binary form
        show_binary(binary);
        //  Swapping two nibbles
        change(binary);
        show_binary(binary);
        int decimal = binary_to_decimal(binary);
        cout << decimal << endl;
    }
}