【BZOJ1088】[SCOI2005]扫雷Mine【枚举】【分类讨论】

发现前两格就可以确定以后的状态了。


枚举前两格状态,判断是否可行。


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

typedef short int sint;

const int maxn = 10005;

int n;
sint a[maxn], f[maxn];

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() {
	for(int i = 3; i <= n; i++) {
		f[i] = a[i - 1] - f[i - 1] - f[i - 2];
		if(f[i] < 0) return 0;
	}
	return f[n - 1] + f[n] == a[n];
}

int main() {
	n = iread();
	for(int i = 1; i <= n; i++) a[i] = iread();
	
	int ans = 0;
	if(a[1] == 0) {
		f[1] = f[2] = 0;
		ans += check();
	} else if(a[1] == 1) {
		f[1] = 1; f[2] = 0;
		ans += check();
		for(int i = 1; i <= n; i++) f[i] = 0;
		f[1] = 0; f[2] = 1;
		ans += check();
	} else {
		f[1] = f[2] = 1; ans += check();
	}

	printf("%d\n", ans);
	return 0;
}


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