Submission #4343029

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Source Code Expand

#include<stdio.h>
#include<iostream>
#include<vector>
#include<algorithm>
#include<string>
#include<string.h>
using namespace std;

typedef long long LL;
typedef vector<int> VI;

#define REP(i,n) for(int i=0, i##_len=(n); i<i##_len; ++i)
#define EACH(i,c) for(__typeof((c).begin()) i=(c).begin(),i##_end=(c).end();i!=i##_end;++i)
#define eprintf(...) fprintf(stderr, __VA_ARGS__)

template<class T> inline void amin(T &x, const T &y) { if (y<x) x=y; }
template<class T> inline void amax(T &x, const T &y) { if (x<y) x=y; }
template<class Iter> void rprintf(const char *fmt, Iter begin, Iter end) {
    for (bool sp=0; begin!=end; ++begin) { if (sp) putchar(' '); else sp = true; printf(fmt, *begin); }
    putchar('\n');
}
template<unsigned MOD> struct ModInt {
    static const unsigned static_MOD = MOD;
    unsigned x;
    void undef() { x = (unsigned)-1; }
    bool isnan() const { return x == (unsigned)-1; }
    inline int geti() const { return (int)x; }
    ModInt() { x = 0; }
    ModInt(const ModInt &y) { x = y.x; }
    ModInt(int y) { if (y<0 || (int)MOD<=y) y %= (int)MOD; if (y<0) y += MOD; x=y; }
    ModInt(unsigned y) { if (MOD<=y) x = y % MOD; else x = y; }
    ModInt(long long y) { if (y<0 || MOD<=y) y %= MOD; if (y<0) y += MOD; x=y; }
    ModInt(unsigned long long y) { if (MOD<=y) x = y % MOD; else x = y; }
    ModInt &operator+=(const ModInt y) { if ((x += y.x) >= MOD) x -= MOD; return *this; }
    ModInt &operator-=(const ModInt y) { if ((x -= y.x) & (1u<<31)) x += MOD; return *this; }
    ModInt &operator*=(const ModInt y) { x = (unsigned long long)x * y.x % MOD; return *this; }
    ModInt &operator/=(const ModInt y) { x = (unsigned long long)x * y.inv().x % MOD; return *this; }
    ModInt operator-() const { return (x ? MOD-x: 0); }

    ModInt inv() const {
	unsigned a = MOD, b = x; int u = 0, v = 1;
	while (b) {
	    int t = a / b;
	    a -= t * b; swap(a, b);
	    u -= t * v; swap(u, v);
	}
	if (u < 0) u += MOD;
	return ModInt(u);
    }
    ModInt pow(long long y) const {
	ModInt b = *this, r = 1;
	if (y < 0) { b = b.inv(); y = -y; }
	for (; y; y>>=1) {
	    if (y&1) r *= b;
	    b *= b;
	}
	return r;
    }
    friend ModInt operator+(ModInt x, const ModInt y) { return x += y; }
    friend ModInt operator-(ModInt x, const ModInt y) { return x -= y; }
    friend ModInt operator*(ModInt x, const ModInt y) { return x *= y; }
    friend ModInt operator/(ModInt x, const ModInt y) { return x *= y.inv(); }
    friend bool operator<(const ModInt x, const ModInt y) { return x.x < y.x; }
    friend bool operator==(const ModInt x, const ModInt y) { return x.x == y.x; }
    friend bool operator!=(const ModInt x, const ModInt y) { return x.x != y.x; }
};

//const LL MOD = 1000000007;
const LL MOD = 998244353;
typedef ModInt<MOD> Mint;
const int MAX = 1100000;
Mint inv[MAX+1], fact[MAX+1], fact_inv[MAX+1];

void init() {
    inv[1] = 1;
    for (int i=2; i<=MAX; i++) inv[i] = inv[MOD%i] * (MOD-MOD/i);

    fact[0] = fact_inv[0] = 1;
    for (int i=1; i<=MAX; i++) {
	fact[i] = fact[i-1] * i;
	fact_inv[i] = fact_inv[i-1] * inv[i];
    }
}

Mint nCk(int n, int k) {
    return fact[n] * fact_inv[k] * fact_inv[n-k];
}

int N, M;

Mint D(int y, int x) {
    if (y < 0 || x < 0) return 0;
    return nCk(x+y, x);
}

Mint solve() {
    Mint B = D(N, M);
    Mint GH = D(N, M-1), GV = D(N-1, M);
    Mint de = 1;

    Mint ans = 0;
    int x = M-1, y = N;
    int dx = 1, dy = 0;

    for (;;) {
	ans += B / de;
//	eprintf("%d %d %d\n", ans.geti(), GH.geti(), GV.geti());

	if (dx == M && dy == N) break;

	if (dx == dy) {
	    GH += D(y, x-1) * D(N-y, M-1-x);
	    GV += D(y-1, x) * D(N-1-y, M-x);
	    x--;
	    dx++;
	} else if (dy == N) {
	    dx++;
	} else {
	    y--;
	    dy++;
	    GH -= D(y, x) * D(N-1-y, M-1-x);
	    GV -= D(y, x) * D(N-1-y, M-1-x);
	}

	B += GH + GV;
	de += 1;
    }

    return ans;
}

void MAIN() {
    init();
    scanf("%d%d", &N, &M);
    if (N > M) swap(N, M);

    Mint ans = solve();

    ans /= D(N, M);

    printf("%d\n", ans.geti());
}

int main() {
    int TC = 1;
//    scanf("%d", &TC);
    REP (tc, TC) MAIN();
    return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘void MAIN()’:
./Main.cpp:134:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d", &N, &M);
                          ^

Judge Result