segmentation fault

[dana18]

If I test this function I have a segmentation fault and I don't know why.

bool bitn(int n, int pos) {
    return (n >> pos)&1; 
}

vector<int> sousEnsemble(const vector<int> &ens, int n) {
    int rem, k=1,binary=0;
    while(n!=0){
        rem=n%2;
        n=n/2;
        binary=binary+rem*k;
        k=k*10;
    }

    vector<int> sousens;
    for(int i=0;i<ens.size();i++){
        if(bitn(binary,i)){
            sousens[i]=ens[i];

        }
        else
            i++;
    }
    if(n==0)
        sousens.clear();
    return sousens;
}
void testSousEnsemble() {
    cout << "Start tests: sous ensemble" << endl;
    ASSERT(egal(sousEnsemble({1,2,3},0),{}));
    ASSERT(egal(sousEnsemble({1,2,3},1),{1}));
    ASSERT(egal(sousEnsemble({1,2,3},2),{2})); // binary 10
    ASSERT(egal(sousEnsemble({1,2,3},3),{1,2})); // binary 11
    ASSERT(egal(sousEnsemble({1,2,3},4),{3})); // binary 100
    ASSERT(egal(sousEnsemble({1,2,3},5),{1,3})); // binary 101
    ASSERT(egal(sousEnsemble({1,2,3},6),{2,3})); // binary 110
    ASSERT(egal(sousEnsemble({1,2,3},7),{1,2,3})); // binary 111
    cout << "Fin tests : sous ensemble" << endl;
}

 

[CptJY]

I think you should dim your vector, or push the value (line 18) :

sousens.push_back(ens[i]);

[coder777]

The reason is that on line 18 sousens is an empty vector. So you cannot assign anything to a certain field. You need to create the vector with the appropriate amount of fields, like so:

vector<int> sousens{ens.size()};

This will invoke the constructor(2):

http://www.cplusplus.com/reference/vector/vector/vector/