• Using constructors in C++

struct point {
    int x, y;
    point() {} // default constructor
    point (int _x, int _y) {
        x = _x;
        y = _y;
    }
};

Another way

struct point {
    int x, y;
    point() {} // default constructor
    point (int x, int y): x(x), y(y) {}
};

• Using Comparison function in C++. For information of operator overloading visit link

struct point {
    int x, y;
    point() {}
    point (int x, int y) : x(x), y(y) {}
    
    // overloading of < operator
    bool operator<(const point &rhs) const{
        // your main logic for the comparator goes here
        return make_pair(x,y) < make_pair(rhs.x, rhs.y);
    }
};

Now A Sample Implementation

Thanks to Break-Neck for pointing out the problem with earlier a <= b in the code of cmp function, see the comment of Break-Neck comment for more details and also see the well commented cmp function.
You can also view link to know more about strict weak ordering in stl.

// please write your includes do not forget to include vector or direcly use include bits/stdc++.h

bool cmp(int a,int b) {
    return a < b;
    // please view the first comment so as to understand the concept of strict weak ordering to be used in comparison if you want to use std:sort etc functions. Strict weak ordering means that specify the case when a is strictly less than b to true, all other cases to false.
  
}

int main() {
    int n;
    cin >> n;

    vector a;

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

    sort (a.begin(), a.end(), cmp);

    for (int i = 0; i < a.size(); i++)
        cout << a[i] << " ";


    return 0;
}

PS. Please do comment if the article was useful or needs some changes or more explanation.