プログラマ専用SNS ミクプラ

コード:

#include <stdio.h>

int main(void)
{
	int W, H;
	int num;
	int i, j, k;
	int WH = 0; //初期化
	int resultW = 1;
	int resultH = 1;
	int resultWH = 1;
	
	scanf("%d", &W);
	scanf("%d", &H);

	WH = (W + H) - 2;

	for (i = 1; i <= W - 1; i++)
	{
		resultW *= i;
	}
	
	for (j = 1; j <= H - 1; j++)
	{
		resultH *= j;
	}

	for (k = 1; k <= WH; k++)
	{
		resultWH *= k;
	}

	num = resultWH / (resultW * resultH);
	
	printf("%d\n", num % 1000000007);

	return 0;
}

コード:

#include <stdio.h>

int main(void)
{
	int W, H;
	unsigned long num;
	int i, j, k;
	int WH = 0; //初期化
	unsigned long resultW = 1;
	unsigned long resultH = 1;
	unsigned long resultWH = 1;
	
	scanf("%d", &W);
	scanf("%d", &H);

	WH = (W + H) - 2;

	for (i = 1; i <= W - 1; i++)
	{
		resultW *= i;
	}
	
	for (j = 1; j <= H - 1; j++)
	{
		resultH *= j;
	}

	for (k = 1; k <= WH; k++)
	{
		resultWH *= k;
	}

	num = resultWH / (resultW * resultH);
	
	printf("%ld\n", num % 1000000007);

	return 0;
}

コード:

#include <stdio.h>
#include <inttypes.h>

#define MOD_BY UINT32_C(1000000007)

/* a * b mod MOD_BY を計算する */
uint32_t mul(uint32_t a, uint32_t b) {
	uint32_t result = 0;
	while (b > 0) {
		/* 今の掛ける数が奇数なら、掛けられる数を結果に足す */
		if ((b & 1) != 0) {
			result += a;
			if (result >= MOD_BY) result -= MOD_BY;
		}
		/* 掛ける数を2で割る */
		b >>= 1;
		/* 掛けられる数を2倍にする */
		a <<= 1;
		if (a >= MOD_BY) a -= MOD_BY;
	}
	return result;
}

/* pow(a, n) mod MOD_BY を計算する */
uint32_t powint(uint32_t a, uint32_t n) {
	uint32_t result = 1;
	while (n > 0) {
		if ((n & 1) != 0) result = mul(result, a);
		n >>= 1;
		a = mul(a, a);
	}
	return result;
}

/* a / b mod MOD_BY を計算する */
uint32_t div(uint32_t a, uint32_t b) {
	/* フェルマーの小定理より、MOD_BYが素数の時bの逆元はpow(b, MOD_BY - 2) */
	return mul(a, powint(b, MOD_BY - 2));
}

int main(void)
{
	int W, H;
	uint32_t num;
	int i, j, k;
	int WH = 0; //初期化
	uint32_t resultW = 1;
	uint32_t resultH = 1;
	uint32_t resultWH = 1;
	
	if (scanf("%d", &W) != 1) return 1;
	if (scanf("%d", &H) != 1) return 1;

	WH = (W + H) - 2;

	for (i = 1; i <= W - 1; i++)
	{
		resultW = mul(resultW, i);
	}
	
	for (j = 1; j <= H - 1; j++)
	{
		resultH = mul(resultH, j);
	}

	for (k = 1; k <= WH; k++)
	{
		resultWH = mul(resultWH, k);
	}

	num = div(resultWH, mul(resultW, resultH));
	
	printf("%"PRIu32"\n", num);

	return 0;
}