C++ : Recursion with a vector

Question

I will like some help, the code used to work, now it doesn't. Help. The purpose is for the user to see the vector backwards using a recursion.

int listar(int v[5], int l); 

void main(){ 
    int vector[5]={1,2,3,4,5}; 
    listar(vector,-1); 
} 

int listar(int v[5],int l){ 
    int n=0; 
    if (n<=5){ 
        cout<< listar(v, n+1)<< endl; 
    return v[n]; 
    } 
return v[5];

Could you elaborate on your comment "...the code used to work, now it doesn't"? It is difficult to help without knowing about your problem. — Santanu C, Nov 06 '13 at 03:54
Did you mean to make an array of 5 vectors or were you looking to have one vector with 5 items in it? — Retired Ninja, Nov 06 '13 at 03:56
Let me guess... Does it just give a stack overflow and print nothing? — paddy, Nov 06 '13 at 03:59

score 0 · Answer 1 · answered Nov 06 '13 at 03:58

0

In the method int listar(int v[5],int l){ you are not using the parameter l at all. Shouldn't the code be using that instead of making n=0 in each recursive call.

answered Nov 06 '13 at 03:58

Pai

282
2
3

score 0 · Answer 2 · answered Nov 06 '13 at 03:59

The code is recursive, You have listar being called by listar.

Recursion is fine, but as you always set n to 0, and then say "if n<5", then you'll get infinite recursion.

I think this is what you mean:

int vector[5]={1,2,3,4,5}; 
    listar(vector,0); 
} 

int listar(int v[5],int l){  
    if (l<=5){ 
        cout<< listar(v, l+1)<< endl;
    }
    return v[l];

But this is quite different

score 0 · Answer 3 · edited May 23 '17 at 10:32

0

This works,

int listar(int v[],int index);

int main(){ 
    int vector[5]={1,2,3,4,5}; 
    listar(vector,(sizeof(vector)/sizeof(*vector))-1); 
    system("pause");
    return 0;
} 

int listar(int v[],int index)
{
    if(index<0) return -1;
    cout<<v[index]<<"\n";
    listar(v,index-1);
    return v[index];
}

Note: You should always use int main as the signature of main function.

edited May 23 '17 at 10:32

Community

1
1

answered Nov 06 '13 at 04:06

mehmet mecek

2,615
2
21
25

score 0 · Answer 4 · answered Nov 06 '13 at 04:08

int listar(vector<int> v, int l); 

int main(){ 
    vector<int> v;
    v.push_back(0);
    v.push_back(1);
    v.push_back(2);
    v.push_back(3);
    v.push_back(4);
    v.push_back(5);
    listar(v,-1); 
    return 0;
} 

int listar(vector<int> v,int n){ 
    if (n<5){ 
        cout<< listar(v, n+1)<< endl; 
    return v[n]; 
    } 
return v[5]; 
}

C++ : Recursion with a vector

4 Answers4