ABC145 D - Knight
備忘録
問題
回答
import sys import os import math import bisect import itertools import collections import heapq import queue import array import time import datetime # 時々使う # import numpy as np # from decimal import Decimal, ROUND_HALF_UP # from scipy.sparse.csgraph import csgraph_from_dense, floyd_warshall # 再帰の制限設定 sys.setrecursionlimit(10000000) def ii(): return int(sys.stdin.buffer.readline().rstrip()) def il(): return list(map(int, sys.stdin.buffer.readline().split())) def it(): return tuple(map(int, sys.stdin.buffer.readline().split())) def fl(): return list(map(float, sys.stdin.buffer.readline().split())) def iln(n): return [int(sys.stdin.buffer.readline().rstrip()) for _ in range(n)] def iss(): return sys.stdin.buffer.readline().decode().rstrip() def sl(): return list(map(str, sys.stdin.buffer.readline().decode().split())) def isn(n): return [sys.stdin.buffer.readline().decode().rstrip() for _ in range(n)] def lcm(x, y): return (x * y) // math.gcd(x, y) # MOD = 10 ** 9 + 7 MOD = 998244353 INF = float('inf') def combination(n, r, mod=10**9+7): n1, r = n+1, min(r, n-r) numer = denom = 1 for i in range(1, r+1): numer = numer * (n1-i) % mod denom = denom * i % mod return numer * pow(denom, mod-2, mod) % mod def main(): if os.getenv("LOCAL"): sys.stdin = open("input.txt", "r") X, Y = il() if (X + Y) % 3 != 0: print(0) exit() n = (-1 * X + 2 * Y) // 3 m = (2 * X - Y) // 3 if n < 0 or m < 0: print(0) exit() print(combination(n + m, n)) if __name__ == '__main__': main()
