Debugging segmentation fault while sorting - c++11

Question

I am asking again with details:
https://stackoverflow.com/questions/33265241/reason-of-segmentation-fault-while-sorting?noredirect=1#comment54333476_33265241
What is the problem in this comparator?
inline bool comp(const vector<int>& a,const vector<int>& b){
for(int i=0;i<a.size() and i<b.size();i++){
if(a[i]<b[i])return 1;
if(a[i]>b[i])return 0;
}
return a.size()<=b.size();
}
I am getting segmentation fault while sorting a vector<vector<int> > using this function as comparator method?
EDIT : Sorry for putting the non-detailed question.
here is the problem statement from interviewbit
https://www.interviewbit.com/courses/programming/topics/backtracking/problems/comb/
inline bool comp(const vector<int>& a,const vector<int>& b){
for(int i=0;i<a.size() and i<b.size();i++){
if(a[i]<b[i])return 1;
if(a[i]>b[i])return 0;
}
return a.size()<=b.size();
}
vector<vector<int> > Solution::combinationSum(vector<int> &A, int B) {
std::sort(A.begin(), A.end());
A.erase(
std::unique(A.begin(), A.end()),
A.end());
/// T[i] : tells us if target i can be achieved or not.
bool T[B+1];
fill(T,T+B+1,0);
T[0]=1;
for(int i=1;i<=B;i++){
for(int j=0;j<A.size() and !T[i];j++){
if(i-A[j]>=0 and T[i-A[j]]){
T[i]=1;
}
}
}
/// Final answer is r[B];
vector< vector<int> > r[B+1];
r[0].push_back(vector<int>());
for(int i=1;i<=B;i++){
if(T[i]){
for(int j=0;j<A.size();j++){
if(i-A[j]>=0 and T[i-A[j]]){
for(int k=0; k<r[i-A[j]].size() ;k++){
vector<int> d=r[ i-A[j] ][ k ];
d.push_back(A[j]);
r[i].push_back(d);
}
}
}
}
}
for(int i=0;i<r[B].size();i++){
sort(r[B][i].begin(),r[B][i].end());
}
cerr << "comming here " << endl;
sort(r[B].begin(),r[B].end(),comp);
cerr << "not reaching here " << endl;
if(r[B].size()==0)return r[B];
vector< vector<int> > ans(1,r[B][0]);
for(int i=1;i<r[B].size();i++){
if(!comp(r[B][i],r[B][i-1])){
ans.push_back(r[B][i]);
}
}
return ans;
}
This code was giving seg fault for input
A : [ 10, 14, 4, 8, 19, 10, 5, 7, 20, 11 ]
B : 31
but on my computer I worked fine.
PS : later I realized that std::vector has < operator and > operator defined which sorts all the vectors in lexicographic order.
sort(r[B].begin(),r[B].end());
Now I wonder why's there segfault on interviewbit platform and not my pc.
General question: What is the reason for these segmentation faults due to bad comparison functions.
for any comparison function f, such that f(a,b) and f(b,a) both returns 0, It will lead to segfault in most cases.
To stack overflow : what is the problem with you guys, you don't let my questions stand for a few hours. Please, before putting anything to hold just think that the user may update the question soon with some more information. Let question stay for at least 24 hrs. Some of us sleep at "night". I asked this question because sometimes bad comparators in sorting can segmentation faults.