runtime error: reference binding to null pointer of type 'int' (stl_vector.h)

Question

Observing a runtime error when trying to run the below code !!

Line 1034: Char 9: runtime error: reference binding to null pointer of type '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

#include <algorithm>
#include <climits>
#include <vector>
class Solution {
public:
    int minimumTotal(vector<vector<int> > &triangle) {
        vector< vector<int> >  soln(1000, vector<int>(0)) ;
        vector< vector<int> >  index(1000, vector<int>(0)) ;
        int ans = INT_MIN ;
        int tmp = 0;
        int ind = 0;
        soln[0][0]=triangle[0][0];
        index[0][0]=0;
        int triangle_size = int(triangle.size());
        for (int i = 1 ; i < triangle_size ; i++) {
            int soln_size = int(soln[i-1].size());
            for (int j = 0; j < soln_size ; j=j+2) {
                ind = index[i-1][j];
                tmp = soln[i-1][j] + triangle[i][ind];
                if (tmp > ans) {
                    ans=tmp;
                }
                soln[i][j] = tmp;
                index[i][j] = ind;
                tmp = soln[i-1][j] + triangle[i][ind+1];
                if (tmp > ans) {
                    ans=tmp;
                }
                soln[i][j+1] = tmp;
                index[i][j+1] = ind+1;            
            }
        }
        return ans;
    }
};

LIU Qingyuan · Accepted Answer · 2021-03-04 05:46:10Z

1

    int minimumTotal(vector<vector<int> > &triangle) {
        vector< vector<int> >  soln(1000, vector<int>(0)) ;
        vector< vector<int> >  index(1000, vector<int>(0)) ;
        int ans = INT_MIN ;
        int tmp = 0;
        int ind = 0;
 >>>>   soln[0][0]=triangle[0][0]
 >>>>   index[0][0]=0;

Here. soln is a vector of 1000 vector of size 0, soln[0] is a vector of size 0, so soln[0][0] is out of range. Accessing it is a UB.

answered Mar 4, 2021 at 5:46

LIU Qingyuan

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1 Comment

LIU Qingyuan Over a year ago

If you want to create a vector contains one zero, then it is std::vector<int> a{0}; instead of std::vector<int> a(0);.

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