EDIT : Turns out by default when the front end code was updated, on all safari browsers it was shifted to mobile mode. So I just had to switch it back (I know this cuz the post had 13 upvotes once.If you still feel this post has absolutely screwed your time then keep downvoting ! No matter what I ask/do that's the only thing I ever got. Go ahead.

Dear MikeMirzayanov All of a sudden today in Safari browser, the side panel as well as the menu tab in the home screen disappeared. Its a bug in front end CSS Javascript. Please look into it Thanks !

I was not able to find an option to see the test cases on which my submission failed. Recently here for example https://atcoder.jp/contests/arc106/submissions/17874024 there are 2 tc which I didn't pass. So maybe At Coder's principles are that if you need to struggle to debug and that's how you improve. But there should be a way to at least generate those locally and just see what's failing.

Is it possible and I am not able to find or is nobody able to do that ?

So I was watching Errichto stream if At Coder Educational DP contest. I understood the transition and the base case but not the filling order. I tried messing with the order of the 3 nested for loops to fill up the table. Some permutations work and some don't .I was just wondering if anyone can help me understand why is that when you make the smaller_taken : {false, true} as the innermost loop we get wrong answer but when it is the second or the outer loop we get correct answer ?

Also I have another question in general to you all. Do you guys just test all orders, see which one passes test cases and then submit that or do you like spend time figuring out the details.

Now I do understand when the transition expression is something like dp[l] = l * dp[l-1] then clearly you need to fill from left to right but that's not always the case. So how do you go about it ?

Problem: https://atcoder.jp/contests/dp/tasks/dp_s

Solution (from the video lecture):

#include <bits/stdc++.h>

#define forn(i, n) for(int i=0; i<n; ++i)

using ll = long long;

using namespace std;

const int mod = 1e9 + 7;

void add_self(int &a, int b) {
	a += b;
	if(a >= mod)
		a -= mod;
}

void solve() {
	
	string k;
	cin >> k;

	int D;
	cin >> D;

	int len = k.size();

	vector<vector<int>>dp(D, vector<int>(2));

	dp[0][0] = 1;

	for(int where = 0; where < len; ++where) {
		vector<vector<int>> new_dp(D, vector<int>(2));

		for(int sum = 0; sum < D; ++sum) {	
			for(bool smaller_taken: { false, true }) {	// this cannot be made innermost for loop why?			
				for(int digit = 0; digit < 10; ++digit) {	

					if(digit > (k[where] - '0') && !smaller_taken) {
						break;
					}

					add_self(new_dp[(sum+digit) % D][smaller_taken || digit < (k[where] - '0')],
					 	dp[sum][smaller_taken]);
				}
			}
		}

		dp = new_dp;
	}

	int answer = (dp[0][false] + dp[0][true]) % mod;
	--answer;
 
	if(answer == -1)
		answer = mod - 1;

	cout << answer << "\n";

}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);

	// int t;
	// cin >> t;

	// while(t--)
		solve();
	
}

Errichto's YouTube channel Stream link: https://youtu.be/FAQxdm0bTaw?t=11154

Also wanna mention that I like this iterative solution than the recursive ones that exist out there on the internet.