Such an error might come because while your program is still in process of exiting the recursion, it might be accessing an array index which is not there. This might be just over the largest possible index, and therefore declaring a little larger array than required might work.

I have a different approach than suggested and it is getting 70 points and is not passing just one test case of the smaller sub-task. Please find a test case for which the test case fails or find the error.

My approach: At each position while moving forward, we have three choices to go to the next square or the next to the next or start moving backward.

While moving backward though, we have just two choices, but we should additionallt necessarily end at the first square.

#include <bits/stdc++.h>

using namespace std;

#define ll long long

#define tc ll t; cin>>t; while(t--)

#define io ios::sync_with_stdio(false),cin.tie(NULL),cout.tie(NULL);