Create team reference document (PDF

generate_pdf/custom/kactl_template.cpp

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+#include <bits/stdc++.h>
+using namespace std;
+
+#define rep(i, a, b) for(int i = a; i < (b); ++i)
+#define all(x) begin(x), end(x)
+#define sz(x) (int)(x).size()
+typedef long long ll;
+typedef pair<int, int> pii;
+typedef vector<int> vi;
+
+int main() {
+	cin.tie(0)->sync_with_stdio(0);
+	cin.exceptions(cin.failbit);
+}

generate_pdf/custom/kactl_troubleshoot.md

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+Pre-submit: Write a few simple test cases if sample is not enough. Are time limits close? If so, generate max cases. Is the memory usage fine? Could anything overflow? Make sure to submit the right file.
+
+Wrong answer: Print your solution! Print debug output, as well. Are you clearing all data structures between test cases? Can your algorithm handle the whole range of input? Read the full problem statement again. Do you handle all corner cases correctly? Have you understood the problem correctly? Any uninitialized variables? Any overflows? Confusing N and M, i and j, etc.? Are you sure your algorithm works? What special cases have you not thought of? Are you sure the STL functions you use work as you think? Add some assertions, maybe resubmit. Create some testcases to run your algorithm on. Go through the algorithm for a simple case. Go through this list again. Explain your algorithm to a teammate. Ask the teammate to look at your code. Go for a small walk, e.g. to the toilet. Is your output format correct? (including whitespace) Rewrite your solution from the start or let a teammate do it.
+
+Runtime error: Have you tested all corner cases locally? Any uninitialized variables? Are you reading or writing outside the range of any vector? Any assertions that might fail? Any possible division by 0? (mod 0 for example) Any possible infinite recursion? Invalidated pointers or iterators? Are you using too much memory? Debug with resubmits (e.g. remapped signals, see Various).
+
+Time limit exceeded: Do you have any possible infinite loops? What is the complexity of your algorithm? Are you copying a lot of unnecessary data? (References) How big is the input and output? (consider scanf) Avoid vector, map. (use arrays/unordered_map) What do your teammates think about your algorithm?
+
+Memory limit exceeded: What is the max amount of memory your algorithm should need? Are you clearing all data structures between test cases?

generate_pdf/custom/python_template.py

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+import sys
+# Avoid automatic flushes
+input = lambda:sys.stdin.readline().rstrip()

generate_pdf/custom/useful_stuff_in_python.py

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+# --- Fractions ---
+from fractions import Fraction
+
+f = Fraction(6, 8)  # Automatically simplifies to 3/4
+print(f)  # 3/4
+print(f.numerator, f.denominator)  # 3 4
+
+
+# --- Decimal (High Precision) ---
+from decimal import Decimal, getcontext
+
+getcontext().prec = 30  # Set precision
+print(Decimal(1) / Decimal(7))  # 0.142857142857142857142857142857
+print(Decimal('0.1') + Decimal('0.2'))  # 0.3 (exact)
+
+
+# --- Output Formatting & Floating Point Decimals ---
+val = 5.12399
+print(f'{val:.4f}')  # 5.1240 (rounds to 4 decimals)
+
+# Integer zero-padding example
+num = 42
+print(f'{num:05d}')  # 00042 (zero-pad with <= 5 zeros)
+
+
+# --- Sys Settings & File / Stream I/O ---
+import sys
+
+# Print with flush
+# Note that calling input() also flushes
+# Warning: flushing can be slow
+print('Hello world', flush=True)
+
+# Read input without flushing
+input = lambda: sys.stdin.readline().rstrip()
+
+# Reading all tokenized inputs at once.
+# Fastest way to read input in Python
+# input_data = sys.stdin.read().split()
+
+# Increase recursion depth for deep DFS
+# Warning: May not work as expected!
+# Consider making use of bootstrap.py instead
+sys.setrecursionlimit(200000)  
+
+# Allow huge int-to-string conversions
+# Default limit is 4300 digits
+sys.set_int_max_str_digits(100000)  
+
+# Print to stderr
+print('Debug message', file=sys.stderr)
+
+# Reading from / Writing to files:
+# with open('input.txt', 'r') as fin, open('output.txt', 'w') as fout:
+#     content = fin.read()
+#     fout.write(content)
+
+
+# --- Heapq (Min-Heap) ---
+import heapq
+
+h = [3, 1, 4, 1, 5, 9]
+heapq.heapify(h)  # Transforms list into a min-heap in-place
+heapq.heappush(h, 2)  # Push item
+print(heapq.heappop(h))  # Pop smallest item
+print(h[0])  # Peek at current smallest item
+
+
+# --- Collections (defaultdict, Counter) ---
+from collections import Counter, defaultdict
+
+d = defaultdict(list)
+d['key'].append(10)
+print(d['key'])  # [10]
+print(d['missing_key'])  # [] (automatically created)
+
+c = Counter('abracadabra')
+print(c)  # Counter({'a': 5, 'b': 2, 'r': 2, 'c': 1, 'd': 1})
+print(c.most_common(2))  # [('a', 5), ('b', 2)]
+
+
+# --- Random ---
+import random
+
+random.seed(42)
+print(random.randint(1, 10))  # Random int [a, b] inclusive
+print(random.randrange(0, 10, 2))  # Random from range(start, stop, step)
+print(random.choice(['apple', 'banana', 'cherry']))  # Random element from sequence
+print(random.uniform(1.0, 5.0))  # Random float between a and b inclusive
+print(random.getrandbits(8))  # Random integer with k random bits
+
+
+# --- Itertools ---
+import itertools
+
+P = itertools.permutations('ABC', 2)
+print(*P)  # ('A', 'B') ('A', 'C') ('B', 'A') ('B', 'C') ('C', 'A') ('C', 'B')
+
+C = itertools.combinations('ABC', 2)
+print(*C)  # ('A', 'B') ('A', 'C') ('B', 'C')
+
+CR = itertools.combinations_with_replacement('ABC', 2)
+print(*CR)  # ('A', 'A') ('A', 'B') ('A', 'C') ('B', 'B') ('B', 'C') ('C', 'C')
+
+
+# --- Memoisation ---
+from functools import cache
+
+@cache  # Automatically memoises return values
+def fib(n):
+  return n if n < 2 else fib(n - 1) + fib(n - 2)
+
+print(fib(50))
+
+
+# --- Bit Operations (bit_length, bit_count) ---
+x = 5  # in binary 0b101
+print(x.bit_length())  # 3 (number of bits needed to represent x)
+print(x.bit_count())  # 2 (number of set bits / popcount, Python 3.10+)
+
+
+# --- Alphabet & Character Checks ---
+import string
+
+print(string.ascii_lowercase)  # abcdefghijklmnopqrstuvwxyz
+print(string.ascii_uppercase)  # ABCDEFGHIJKLMNOPQRSTUVWXYZ
+
+vowels = set('aeiouAEIOU')
+print('a' in vowels)  # True
+print('b'.isalpha())  # True
+
+s = '  hello world  '
+print(s.strip())  # 'hello world' (strips both ends)
+print(s.lstrip())  # 'hello world  ' (strips left)
+print(s.rstrip())  # '  hello world' (strips right)
+
+words = ['apple', 'banana', 'cherry']
+print('-'.join(words))  # 'apple-banana-cherry'
+
+print('42'.ljust(5, '0'))  # '42000' (left-justified, padded)
+print('42'.rjust(5, '0'))  # '00042' (right-justified, padded)
+
+text = 'apple,banana,cherry'
+print(text.split(','))  # ['apple', 'banana', 'cherry'] (with argument)
+print('  a   b  c '.split())  # ['a', 'b', 'c'] (without argument, splits by whitespace)
+
+# Substring check & counting
+print('ana' in 'banana')  # True (checks if substring exists)
+print('bananana'.count('ana'))  # 2 (counts non-overlapping occurrences: b[ana]n[ana])
+
+
+# --- Bisect (Binary Search) ---
+import bisect
+
+arr = [1, 3, 3, 3, 5, 7]
+print(bisect.bisect_left(arr, 3))  # 1 (first insertion index)
+print(bisect.bisect_right(arr, 3))  # 4 (last insertion index)
+
+
+# --- Math Module & Division Tricks ---
+import math
+
+print(math.pi)  # 3.141592653589793
+print(math.gcd(24, 36))  # 12
+print(math.lcm(4, 6))  # 12
+print(math.comb(5, 2))  # 10 (nCr / binomial coefficient)
+print(math.perm(5, 2))  # 20 (nPr)
+print(math.isqrt(10))  # 3 (integer square root)
+print(math.inf)  # Infinity representation
+
+# Division types:
+a, b = 7, 3
+print(a // b)  # 2 (floored division)
+print(0 -- a // b))  # 3 (ceiled division)
+
+
+# --- Prime Sieve (Sieve of Eratosthenes) ---
+limit = 30
+is_prime = [1] * limit
+is_prime[0] = is_prime[1] = 0
+for i in range(2, int(limit**0.5) + 1):
+  if is_prime[i]:
+    for j in range(i * i, limit, i):
+      is_prime[j] = 0
+
+primes = [i for i, p in enumerate(is_prime) if p]
+print(primes)  # [2, 3, 5, 7, 11, 13, 17, 19, 23, 29]