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# N Loop

Generalize the for loop to be nested n-dimensionally. Provide capability to generalize and print any computational sequence
$_nC_k$
.
EXAMPLE
n_for(3,3)
0 1 2
0 1 3
0 2 3
1 2 3
n_for(4,4)
0 1 2 3
0 1 2 4
0 1 3 4
0 2 3 4
1 2 3 4
Current progress: working with 1 and 3's. There is an issue on how index gets adjusted.
void manual_for_n1() {
const int limit = 1;
for (int i = 0; i <= limit; i++) {
cout << i << endl;
}
cout << "__________________________\n\n";
}
void manual_for_n2() {
const int limit = 2;
for (int i = 0; i <= limit; i++) {
for (int j = i + 1; j <= limit; j++) {
cout << i << " " << j << endl;
}
}
cout << "__________________________\n\n";
}
void manual_for_n3() {
const int limit = 3;
for (int i = 0; i <= limit; i++) {
for (int j = i + 1; j <= limit; j++) {
for (int k = j + 1; k <= limit; k++) {
cout << i << " " << j << " " << k << endl;
}
}
}
cout << "__________________________\n\n";
}
void manual_for_n4() {
const int limit = 4;
for (int i = 0; i <= limit; i++) {
for (int j = i + 1; j <= limit; j++) {
for (int k = j + 1; k <= limit; k++) {
for (int l = k + 1; l <= limit; l++) {
cout << i << " " << j << " " << k << " " << l << endl;
}
}
}
}
cout << "__________________________\n\n";
}
/*
* ijk: maintains the current state of for loop variables (i,j,k...)
* ijk_ref: points current state (i,j,k...) to the previous state + 1
* go_till: fixed integer for for loop terminating condition
* index: what variable (i,j,k...) is being reference at a given moment in for loop
* num_for: fixed size of number of for loops
* counter: counts up to limit num_for to end number of for loops
*
*/
void n_for_rec(vector<int> &ijk, vector<int*> &ijk_ref, const int &go_till, int index, const int num_for, int &counter)
{
if (counter < num_for) {
for (ijk[index] = *ijk_ref[index] + 1; ijk[index] < go_till; ++ijk[index], ++index) {
n_for_rec(ijk, ijk_ref, go_till, index + 1, num_for, ++counter);
for (int j : ijk) cout << j << " ";
cout << endl;
}
}
}
void n_for(const int num_for, const int go_till) {
int i = -1;
vector<int> ijk(num_for);
vector<int*> ijk_ref(num_for);
ijk_ref[0] = &i;
for (int i = 1; i < num_for; i++)
ijk_ref[i] = &(ijk[i - 1]);
int index = 0, counter = 0;
n_for_rec(ijk, ijk_ref, go_till, index, num_for, counter);
cout << "__________________________\n\n";
}
int main()
{
//manual_for_n1();
//n_for(1, 1);
manual_for_n2();
n_for(2, 2);
manual_for_n3();
n_for(3, 3);
manual_for_n4();
n_for(4, 4);
}