向量中的分割错误

Question

I am practicing a dynamic programming problem called the gold mine problem onGeeksForGeeks
My code

#include <iostream>
#include<vector>
using namespace std;
int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int test,i,max_rows,max_columns,temp;
    cin >> test;
    for(i=1;i<=test;i++)
    {
        cin>>max_rows>>max_columns;
        vector<vector<int>> v;//(20,vector<int>(20,0));
        for(int row = 0; row<max_rows; row++)
        {
            v.push_back(vector<int>());
            for(int column = 0; column<max_columns; column++)
            {
                cin>>temp;
                v[row].push_back(temp);
            }
        }
        for(int column = max_columns-1;column>=0;column--)
        {
            for(int row=0; row<max_rows;row++)
            {
                int add;
                if(column>=(max_columns-1))
                    add = 0;
                else if(row==0)
                    add = max(v[row][column+1], v[row+1][column+1]);
                else if(row==(max_rows-1))
                    add = max(v[row-1][column+1], v[row][column+1]);
                else if(row>(max_rows-1))
                    add = 0;
                else
                    add = max(v[row-1][column+1], max(v[row][column+1],v[row+1][column+1]));
                v[row][column]+= add;
            }
        }
        int max_value = 0;
        for(int row = 0;row<max_rows;row++)
            if(max_value<v[row][0])
                max_value = v[row][0];
        
        cout<<max_value<<endl;
    }
    return 0;
}

On some unknown testcase I'm getting a Segmentation Fault

Runtime Error: Runtime ErrorSegmentation Fault (SIGSEGV)

I am sure that my code is not accessing any negative indexes as the code works when I initialize the vector<vector<int>> with the constructor below. (I choose 20 due to the limits of the matrix size in the problem)

vector<vector<int>> v(20,vector<int>(20,0));

I fail to understand why I'm getting segmentation fault because I'm making sure no indexes outside the range are accessed with my if-else ladder.

Answer 1

                else if(row==0)
                    add = max(v[row][column+1], v[row+1][column+1]);

The problem specification clearly states that it is perfectly valid to have only one row. But this code assumes that there are at least two rows.

This can (and likely will) crash if the input is 1 1 3 1 2 3 , which is perfectly valid input.