Perfect square

#include<iostream>

using namespace std;


int** allocate(int l){
    int** a = new int*[l];
    for(int i = 0; i < l; i++)
        a[i] = new int[l];
    return a;
}

int sumX(int** a, int l, int x){
    int sum = 0;
    for(int y = 0; y < l; y++) sum += a[x][y];
    return sum;
}

int sumY(int** a, int l, int y){
    int sum = 0;
    for(int x = 0; x < l; x++) sum += a[x][y];
    return sum;
}

int sumDP(int** a, int l){
    int sum = 0;
    for(int i = 0; i < l; i++) sum += a[i][i];
    return sum;
}

int sumDS(int** a, int l){
    int sum = 0, n = l;
    for(int i = 0; i < l; i++) sum += a[i][--n];
    return sum;
}

bool verify(int** a, int l){
    bool b = true;
    int sum = sumX(a, l, 0), n = 1;

    while((n < l) && b){
        b = sumX(a, l, n) == sum;
        n++;
    }

    n = 0;
    while((n < l) && b){
        b = sumY(a, l, n) == sum;
        n++;
    }

    return b && (sumDP(a, l) == sum) && (sumDS(a, l));
}

void fill(int** a, int l, int n){
    for(int x = 0; x < l; x++)
        for(int y = 0; y < l; y++)
            a[x][y] = n;
}

void print(int** a, int l){
    for(int x = 0; x < l; x++) {
        for(int y = 0; y < l; y++)
            cout << a[x][y] << "\t";
        cout << endl;
    }
}

int nextD(int n, int l){
    if(--n < 0) n = l - 1;
    return n;
}


int nextI(int n, int l){
    if(++n >= l) n = 0;
    return n;
}


int main(){
    int l, i = 1, xNew, yNew, xOld, yOld = 0;

    do{
        cin >> l;
    }while((l % 2) == 0);

    int** a = allocate(l);
    fill(a, l, 0);
    xOld = l / 2;
    a[xOld][yOld] = 1;

    while(++i <= (l * l) ){

        xNew = nextD(xOld, l);
        yNew = nextD(yOld, l);

        if(a[xNew][yNew] == 0) {

            a[xNew][yNew] = i;
            xOld = xNew;
            yOld = yNew;

        } else {

            yOld = nextI(yOld, l);
            a[xOld][yOld] = i;

        }

    }

    print(a, l);
    if(verify(a, l)) cout << "True\n"; else cout << "False\n";
}