【POJ3254】【BZOJ1725】Corn Fields【状压DP】

http://poj.org/problem?id=3254

自己写出的第一道状压DP，竟然1A了。

/* Footprints In The Blood Soaked Snow */
#include <cstdio>
#include <algorithm>

using namespace std;

const int maxn = 13, maxs = (1 << 12) + 5, p = 100000000;

int n, m, g[maxn], dp[maxn][maxs];

inline int iread() {
	int f = 1, x = 0; char ch = getchar();
	for(; ch < '0' || ch > '9'; ch = getchar()) f = ch == '-' ? -1 : 1;
	for(; ch >= '0' && ch <= '9'; ch = getchar()) x = x * 10 + ch - '0';
	return f * x;
}

inline bool check(int s) {
	return (s & (s << 1)) ? 0 : 1;
}

inline bool fit(int s, int i) {
	return (s & g[i]) ? 0 : 1;
}

inline bool check(int s1, int s2) {
	return (s1 & s2) ? 0 : 1;
}

int main() {
	n = iread(); m = iread(); int S = 1 << m;

	for(int i = 1; i <= n; i++) for(int j = 1; j <= m; j++) if(!iread())
		g[i] |= 1 << (j - 1);
	
	for(int i = 0; i < S; i++) if(check(i) && fit(i, 1)) dp[1][i] = 1;

	for(int i = 2; i <= n; i++)
		for(int j = 0; j < S; j++) if(check(j) && fit(j, i))
			for(int k = 0; k < S; k++) if(check(k) && fit(k, i - 1)) {
				if(!check(j, k)) continue;
				dp[i][j] = (dp[i][j] + dp[i - 1][k]) % p;
			}

	int ans = 0;
	for(int i = 0; i < S; i++) if(check(i)) ans = (ans + dp[n][i]) % p;
	printf("%d\n", ans);
	return 0;
}