CODEWITHSUNDEEP
c++
Sakshi Singh
Sakshi Singh

Reputation: 1

how to resolve the error reference binding to null pointer of type value

 //this is my code that i have written 
vector<vector<int>> generate(int numRows) {

        vector<vector<int>>ans;

        ans[0].push_back(1);
        if(numRows==1) return ans;

        ans[1].push_back(1);
        ans[1].push_back(1);

        if(numRows==2) return ans;

        for(int i=2;i<=numRows-1;i++){
            for(int j=0 ; j<= ans [i] . size() - 2 ; j++){

                int x= ans [i][j] + ans [i][j+1];
                ans [i+1].push_back(x);
            }
            ans [i+1].insert(ans [i+1].begin(),1);
            ans [i+1].insert(ans [i+1].end(),1);
        }

        return ans;
}

this code showing below error.

Line 1034: Char 9: runtime error: reference binding to null pointer of type 'std::vector<int, std::allocator<int>>' (stl_vector.h)
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /usr/bin/../lib/gcc/x86_64-linux-gnu/9/../../../../include/c++/9/bits/stl_vector.h:1043:9

Upvotes: 0

Views: 1018

Answers (1)

foragerDev
foragerDev

Reputation: 1409

As vector stores data on heap internally which can grow and shrink based on your usage. But in your case, you made an empty vector so it did not allocate any memory. To avoid this error you have to provide size to vector constructor or push back empty vector on every index you want to use. so you might want to do this:

    std::vector<vector<int>> ans(numRows);
    ans[0].push_back(1);

This will work.

Upvotes: 1

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