Square Matrix Indices Tricks using C++

#include <bits/stdc++.h>

using namespace std;

void Print(vector<vector<int>> a) {
    for (int i = 0; i < (int) a.size(); i++) {
        for (int j = 0; j < (int) a[i].size(); j++) {
            cout << a[i][j] << " ";
        }
        cout << '\n';
    }
    cout << '\n';
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    // enter size of square matrix
    int n;
    cin >> n;

    // upper-left right triangle:
    vector<vector<int>> a(n, vector<int>(n, 0));
    a[0][0] = 1;
    for (int i = 1; i + 1 < n; i++) {
        for (int j = i; j >= 0; j--) {
            a[i - j][j] = 1;
        }
    }
    Print(a);

    // bottom-right right triangle
    a[n - 1][n - 1] = 1;
    for (int j = n - 2; j > 0; j--) {
        for (int i = 0; i < n - j; i++) {
            a[n - 1 - i][j + i] = 1;
        }
    }
    Print(a);

    // other diagonal
    for (int i = n - 1; i >= 0; i--) {
        a[i][n - 1 - i] = 1;
    }
    Print(a);
    return 0;
}