Submission #2038316

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Source Code Expand

#include<stdio.h>
#include<vector>
#include<algorithm>
using namespace std;
typedef long long ll;
ll mod = 998244353;
#define SIZE 1100000
ll inv[SIZE + 1];
ll kai[SIZE + 1];
ll invkai[SIZE + 1];
void invinit()
{
	inv[1] = 1;
	for (int i = 2; i <= SIZE; i++)
	{
		inv[i] = mod - (mod / i)*inv[mod%i] % mod;
	}
	kai[0] = invkai[0] = 1;
	for (int i = 1; i <= SIZE; i++)
	{
		kai[i] = kai[i - 1] * i%mod;
		invkai[i] = invkai[i - 1] * inv[i] % mod;
	}
}
ll com(ll a, ll b)
{
	if (b < 0 || a < b)return 0;
	return (invkai[b] * invkai[a - b]) % mod*kai[a] % mod;
}
int main()
{
	invinit();
	int x, y;
	scanf("%d%d", &x, &y);
	ll sum = 0;
	ll now = com(x + y, x);
	for (int i = 1; i <= x + y; i++)
	{
		//printf("%lld\n", now);
		sum += now;
		if (i & 1)
		{
			int a = i / 2, b = a + 1;
			ll t = com(a + b, a)*com(x + y - a - b - 1, y - b) % mod*b%mod*inv[a + b] % mod;
			ll s = com(b + b, b)*com(x + y - b - b, y - b) % mod*inv[2] % mod;
			now = (now + mod + s - t * 2 % mod) % mod;
		}
	}
	printf("%lld\n", sum % mod*kai[x] % mod*kai[y] % mod*invkai[x + y] % mod);
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:34:23: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d", &x, &y);
                       ^

Judge Result