восстановление матрицы

#include <iostream>
#include <vector>
#include <random>

using namespace std;

int main() {

    int n, r;
    cin >> n;
    vector <vector <int> > a;
    vector <int> bolean;

    for (int i = 0; i < n * n; i++) {
        bolean.push_back(i + 1);
    }

    for (int i = 0; i < n; i++) {
        vector <int> b;
        a.push_back(b);
        for (int j = 0; j < n; j++) {
            cin >> r;
            a[i].push_back(r);
        }
    }


    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {

            if (a[i][j] != 0) {
                bolean[a[i][j] - 1] = 0;
            }

        }
    }
    for (int i = 0; i < bolean.size(); i++) {
        if (bolean[i] == 0) {
            swap(bolean[i], bolean[bolean.size() - 1]);
            bolean.pop_back();
        }
    }
    for (int i = 0; i < bolean.size(); i++) {
        if (bolean[i] == 0) {
            swap(bolean[i], bolean[bolean.size() - 1]);
            bolean.pop_back();
        }
    }
    for (int i = 0; i < bolean.size(); i++) {
        if (bolean[i] == 0) {
            swap(bolean[i], bolean[bolean.size() - 1]);
            bolean.pop_back();
        }
    }


    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {

            if (a[i][j] == 0) {
                int c = rand() % bolean.size();
                a[i][j] = bolean[c];
                swap(bolean[c], bolean[bolean.size() - 1]);
                bolean.pop_back();
            }

        }
    }

    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            cout << a[i][j] << ' ';
        }
        cout << endl;
    }

    return 0;
}