JOI2013年度予選問題4。15分で解いたので汚いのは許して

JOI-2013-yo-t4.cpp

#include <iostream>
#include <stdlib.h>
#include <stdio.h>

bool atnd(int a, char b) {
	if (b == 'J') {
		if (a >> 0 & 1 == 1) return true;
		else return false;
	} else if (b == 'O') {
		if (a >> 1 & 1 == 1) return true;
		else return false;
	} else if (b == 'I') {
		if (a >> 2 & 1 == 1) return true;
		else return false;
	}
}

bool serial(int a, int b) {
	if (atnd(a,'J') && atnd(b,'J')) return true;
	if (atnd(a,'O') && atnd(b,'O')) return true;
	if (atnd(a,'I') && atnd(b,'I')) return true;
	return false;
}

int main() {
	int N;
	char JOI[1001];
	int dp[1001][8];
	std::cin >> N;
	std::cin >> JOI;
	for (int i = 0; i < 8; i++) {
		if (atnd(i, JOI[0]) && atnd(i, 'J')) dp[0][i] = 1;
		else dp[0][i] = 0;
	}
	for (int i = 1; i < N; i++) {
		for (int j = 0; j < 8; j++) {
			dp[i][j] = 0;
			if (atnd(j, JOI[i])) {
				for (int k = 0; k < 8; k++) {
					if (serial(j, k)) dp[i][j] = (dp[i][j] + dp[i-1][k]) % 10007;
				}
			}
		}
	}
	int ans = 0;
	for (int j = 0; j < 8; j++) {
		ans = (ans + dp[N-1][j]) % 10007;
	}
	std::cout << ans << std::endl;
	return 0;
}