You can ask them just in these posts — it is the most usual way. However try to respect English language to increase chance of being answered, instead of being severely downvoted ;-)

You are not only new, you are also very stupid.

Each problem here was a part of contest. When you solve a problem , see the tutorial , probably you will find some contestants who was discussing these problems after each contest. And as RodionGork said , try to respect English language to increase chance of being answered. Welcome to Codeforces =)

As Druid mentioned you can always look up the tutorial for a problem that was in a competition here, but you can also always ask any questions about any problems you encounter at all, in just these posts (blogs). Codeforces community is friendly and helpful, I have asked questions myself and someone always had the right answer, so if there is any task you are struggling with you can always ask here for help. As previously mentioned, try describing the problem you have in proper English so people can understand and help you (it also irritates a lot of people when they see posts with bad English), and I'm sure you will get the answers you are looking for.

Welcome to Codeforces! :)

What is the means of this in any program #define mod 998244353

What is the different between 1. v.push_back({v[i].first, v[i].second + 1}); Vs 2. v.push_back((v[i].first, v[i].second + 1));

20C][SUBMISSION:239959904 - Dijkstra? please see fails on large test case test case 31 failed. Dijkstra 20c <-problem

#include <iostream>
#include <bits/stdc++.h>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <unordered_map>
#include <deque>
#include <list>
using namespace std;

#define ull unsigned long long
#define ll long long
#define fast_io ios_base::sync_with_stdio(false);cin.tie(NULL)
#define readi(x) ull x;cin>>x

#include<bits/stdc++.h>
using namespace std;


void ulp(int node, vector<int>&parent, vector<int>&ans) {
	if (parent[node] == node) {
		ans.push_back(node);
		return;
	}
	ans.push_back(node);
	ulp(parent[node], parent, ans);
}

void dij(vector<vector<int>>edges, int V) {


	vector<pair<int, int>>adj[V + 1];
	for (auto it : edges) {
		int u = it[0];
		int v = it[1];
		int wt = it[2];
		adj[u].push_back({v, wt});
		adj[v].push_back({u, wt});
	}

	priority_queue < pair<int, int>, vector<pair<int, int>>, greater<pair<int, int>>>pq;
	pq.push({0, 1});

	vector<int>dist(V + 1, 1e9);
	vector<int>parent(V + 1);
	for (int i = 0; i <= V; i++)parent[i] = i;
	dist[1] = 0;
	while (!pq.empty()) {
		auto it = pq.top();
		pq.pop();
		int wt = it.first;
		int node = it.second;
		for (auto it : adj[node]) {
			int adjNode = it.first;
			int adjWt = it.second;
			if (wt + adjWt < dist[adjNode]) {
				parent[adjNode] = node;
				dist[adjNode] = wt + adjWt;
				pq.push({dist[adjNode], adjNode});
			}
		}

	}
	if (dist[V] == 1e9) {
		cout << -1 << endl;
		return;
	}
	vector<int>ans;
	ulp(V, parent, ans);
	reverse(ans.begin(), ans.end());
	for (auto it : ans)cout << it << " ";


}




int main() {
	//uncomment the below for USACO Submission and name the problem name.in etc etc. read more->https://codeforces.com/blog/entry/84772

	// if (fopen("perimeter.in", "r")) {
	// 	freopen("perimeter.in", "r", stdin);
	// 	freopen("perimeter.out", "w", stdout);
	// }

	fast_io;
#ifndef ONLINE_JUDGE
	freopen("INPUT.txt", "r", stdin);
	freopen("Op.txt", "w", stdout);
#endif

	int n, m;
	cin >> n >> m;
	vector<vector<int>>edges;
	while (m--) {
		int a, b, w;
		cin >> a >> b >> w;
		edges.push_back({a, b, w});
	}

	dij(edges, n);

	return 0;
}

please guide me which of the following topics are important for Competitive programming. also if you can share some of the problems/links related to the following topics in mathematics:

Root finding for non linear equations and systems of equation

1 Introduction to Numerical computations and floating point arithmetic

2 Types of errors, significant digits and error propagation.

3 Introduction to iterative methods, initial approximation and intermediate value theorem

4 Iterative Methods based on first degree equation

5 Iterative Methods based on second degree equation: Muller Method

6 Solved Problems using Muller Method

7 Chebyshev Method

8 Solution of the system of non-linear equations using the Newton Raphson method.

** Interpolation**

11 Finite Difference Operators

12 Interpolating polynomials using Finite Difference(Gauss Forward)

13 Interpolating polynomials using Finite Difference(Gauss Backward)

14 Hermite Interpolation

15 Problem solving

16 Tutorial(Problem Solving)

17 Lagrange Bivariate Interpolation

18 Newton’s Bivariate Interpolation for Equispaced Points

19 Inverse Interpolation

Numerical Integration

21 Introduction to Numerical Integration

22 Numerical Integration with known nodes

23 Rombergh Integration

24 Gauss-Legendre Integration

25 Gauss-Chebyshev

26 Gauss-Laguerre and Gauss-Hermite Integration Methods.

27 Problem solving

28 Double Integration by Trapizoidal methods.

29 Double Integration by Simpsons’ methods.

30 Problem solving Numerical Solution of ODEs and PDEs

32 Introduction to the numerical solution of ODEs

33 Initial Value Problems and it’s numerical solutions

34 Milne’s method

35 Boundary Value Problems using Shooting Method

36 Problem Solving

37 Finite Difference approximation of derivatives

38 Using Finite difference methods to solve 1D heat equation using explicitn method(Schmidt Method)

39 Finite difference methods to solve 1Dheat equation using implicit scheme(Crank Nicholson Method)

i don't get it how do i do it without using arithmetic operations please help!!

Problem Statement:

Given 'd' you have to calculate f(d) where , f(d)=2*d(d+1)+1 using bit manipulation. Dont't use +,-,/,* arithmetic operations either. f(d) is only for reference for checking for given d whether f(d) is valid or not.

constraints: 0<=d<=100, 1<=f(d)<=20201

test case1 d=0 op=1; test case2 d=1 op=5; test case3 d=2 op=13 test case4 d=3 op=25 test case5 d=4 op=41

int function(int d){

//don't do -> return 2*d(d+1)+1 instead try to do it using bit manipulation on given 'd' parameter.

}