It has segmentation fault. How to fix it? #include <vector> #include <iostream>

Question

It has segmentation fault. How to fix it?

#include <vector>
#include <iostream>

using namespace std;

vector<int> insert(const vector<int> & prev, int pos, int elem){
   vector<int> v;
  
   for (int i=0; i<pos; i++)
       v.push_back(prev[i]);
   v.push_back(elem);
   for (int i=pos; i<prev.size();i++)
       v.push_back(prev[i]);

   return v;
}

vector<vector<int> > getPermutationssOfOneToN(int n){
   vector<vector<int> > v;
   vector<int> s;
   if (n<=0){
       v.push_back(s);
       return v;
   }
   else{
       vector<vector<int> > v2 = getPermutationssOfOneToN(n-1); // all permutations of {1 .. n-1}
       for (int i=0; i<v2.size(); i++){
           s = v[i]; // s is one permutation of {1 ... n-1}
           for (int j=0; j<=s.size(); j++){
               vector<int> new_perm = insert(s,j,n);
               v.push_back(new_perm);
           }
       }
       return v;
   }
}

void print_vector(const vector<int>& v){
   for (int i=0; i<v.size(); i++)
       cout << v[i] << " ";
   cout << endl;
}

int main(){
   for (int i= 1; i<5; i++){
       cout << "permutationss of {1.." << i << "}:" << endl;
       vector<vector<int> > perms = getPermutationssOfOneToN(i);
       for (vector<vector<int> >::iterator itr=perms.begin(); itr<perms.end(); itr++)
           print_vector(*itr);
   }

}

Explanation / Answer

This is one of the option which solves your problem:

#include <vector>
#include <iostream>
using namespace std;
vector<int> insert(const vector<int> & prev, int pos, int elem){
vector<int> v;
  
for (int i=0; i<pos; i++)
v.push_back(prev[i]);
v.push_back(elem);
for (int i=pos; i<prev.size();i++)
v.push_back(prev[i]);
return v;
}
vector<vector<int> > getPermutationssOfOneToN(int n, vector<vector<int> > v){
vector<int> s;
if (n<=0){
v.push_back(s);
return v;
}
else{
vector<vector<int> > v2 = getPermutationssOfOneToN(n-1, v); // all permutations of {1 .. n-1}
for (int i=0; i<v2.size(); i++){
s = v[i]; // s is one permutation of {1 ... n-1}
for (int j=0; j<=s.size(); j++){
vector<int> new_perm = insert(s,j,n);
v.push_back(new_perm);
}
}
return v;
}
}
void print_vector(const vector<int>& v){
for (int i=0; i<v.size(); i++)
cout << v[i] << " ";
cout << endl;
}
int main(){
for (int i= 1; i<5; i++){
cout << "permutationss of {1.." << i << "}:" << endl;
vector< vector<int> > perms(i, vector<int>(i, 0));
getPermutationssOfOneToN(i, perms);
for (vector<vector<int> >::iterator itr=perms.begin(); itr<perms.end(); itr++)
print_vector(*itr);
}
}

And the other one is:

#include <vector>
#include <iostream>
using namespace std;
vector<int> insert(const vector<int> & prev, int pos, int elem){
vector<int> v;
  
for (int i=0; i<pos; i++)
v.push_back(prev[i]);
v.push_back(elem);
for (int i=pos; i<prev.size();i++)
v.push_back(prev[i]);
return v;
}
vector<vector<int> > getPermutationssOfOneToN(int n){
vector<vector<int> > v(n, vector<int>(1 << n, 0));
vector<int> s;
if (n<=0){
v.push_back(s);
return v;
}
else{
vector<vector<int> > v2 = getPermutationssOfOneToN(n-1); // all permutations of {1 .. n-1}
for (int i=0; i<v2.size(); i++){
s = v[i]; // s is one permutation of {1 ... n-1}
for (int j=0; j<=s.size(); j++){
vector<int> new_perm = insert(s,j,n);
v.push_back(new_perm);
}
}
return v;
}
}
void print_vector(const vector<int>& v){
for (int i=0; i<v.size(); i++)
cout << v[i] << " ";
cout << endl;
}
int main(){
for (int i= 1; i<5; i++){
cout << "permutationss of {1.." << i << "}:" << endl;
vector< vector<int> > perms = getPermutationssOfOneToN(i);
for (vector<vector<int> >::iterator itr=perms.begin(); itr<perms.end(); itr++)
print_vector(*itr);
}
}

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