Competitive Programming Code Templates

Abstract

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A collection of code templates to kickstart the journey of solving interesting problems on Codeforces!

Tip

1. Make sure all inputs are read in in sequence
2. Use at least 64Bit to prevent integer overflow issue, long in Java, long long in CPP
3. Dynamic Array over Array

Java Code Template

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Test Solution.java with test cases inside input.txt

java Solution.java < input.txt

Solution.java when there are multiple inputs in a single test case

Solution.java

import java.util.*;
import java.io.*;
 
public class Solution {
  static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
 
 // Write your solution here
  public static void solve() throws IOException {
    System.out.println("Write your solution inside the solve() method");
    // StringTokenizer st = new StringTokenizer(br.readLine());
    // Integer.parseInt(st.nextToken());
  }
 
  public static void main(String[] args) throws IOException {
    int t = Integer.parseInt(br.readLine());
    
    while(t-- > 0) {
      solve();
    }
  }
}

Solution.java when there is only a single input in a given test case

Solution.java

import java.util.*;
import java.io.*;
 
public class Solution {
  static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
 
 // Write your solution here
  public static void solve() throws IOException {
    System.out.println("Write your solution inside the solve() method");
    // StringTokenizer st = new StringTokenizer(br.readLine());
    // Integer.parseInt(st.nextToken());
  }
 
  public static void main(String[] args) throws IOException  {
    solve();
  }
}

Basic Data Structure Operation Cheatsheet

Java List

Avoid Potential TLE

1. If there are many small segments that need to be printed out one by one, or we need to consolidate many small input string pieces into one string. Consolidate them into one string with StringBuilder. Because string in java is Immutable, concatenating 2 strings require us to create a new string. Example: without StringBuilder Buffer, with StringBuilder Buffer
2. Use BufferedReader, InputStreamReader and StringTokenizer to read in the input, instead of using Scanner

CPP Code Template

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Test Solution.cpp with test cases inside input.txt

g++ -o Solution Solution.cpp && ./Solution < input.txt

Solution.cpp when there are multiple inputs in a single test case

Solution.cpp

#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <string>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <numeric>
#include <functional>
#include <limits>
#include <bitset>
#include <iomanip>
#include <iterator>
#include <cassert>
using namespace std;
typedef long long ll;
 
struct test {
 void solve() {
   cout << "Write your solution inside the solve() method\n";
 }
};
 
int main() {
 ios::sync_with_stdio(false);
 int t;
 cin >> t;
 for (int i = 0; i < t; i++) {
   test().solve();
 }
 return 0;
}

Solution.cpp when there is only a single input in a given test case

Solution.cpp

#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <string>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <numeric>
#include <functional>
#include <limits>
#include <bitset>
#include <iomanip>
#include <iterator>
#include <cassert>
using namespace std;
typedef long long ll;
 
struct test {
 void solve() {
   cout << "Write your solution inside the solve() method\n";
 }
};
 
int main() {
   ios::sync_with_stdio(false);
 
   test().solve();
 
   return 0;
}