_bzoj1026 [SCOI2009]windy数【数位dp】

传送门：http://www.lydsy.com/JudgeOnline/problem.php?id=1026

数位dp果断记忆化搜索，代码量少~ 程序里我用11代表前导零。

#include <cstdio>
#include <cstring>

int A, B, f[15][15][2], a[15], wei;

inline int abs(int aa) {
	return aa > 0? aa: -aa;
}
int dp(int left, int now, char jin) {
	if (f[left][now][jin] != -1) {
		return f[left][now][jin];
	}
	if (!left) {
		return f[left][now][jin] = 1;
	}
	int & rhs = f[left][now][jin];
	rhs = 0;
	if (jin) {
		if (abs(a[left] - now) >= 2) {
			rhs += dp(left - 1, a[left], 1);
		}
		for (int i = 0; i < a[left]; ++i) {
			if (abs(i - now) >= 2) {
				rhs += dp(left - 1, i, 0);
			}
		}
	}
	else if (now == 11) {
		rhs += dp(left - 1, 11, 0);
		for (int i = 1; i < 10; ++i) {
			rhs += dp(left - 1, i, 0);
		}
	}
	else {
		for (int i = 0; i < 10; ++i) {
			if (abs(i - now) >= 2) {
				rhs += dp(left - 1, i, 0);
			}
		}
	}
	return rhs;
}

inline int slove(int n) {
	if (n < 10) {
		return n + 1;
	}
	wei = 0;
	while (n) {
		a[++wei] = n % 10;
		n /= 10;
	}
	memset(f, -1, sizeof f);
	int rt = dp(wei - 1, 11, 0);
	for (int i = 1; i < a[wei]; ++i) {
		rt += dp(wei - 1, i, 0);
	}
	rt += dp(wei - 1, a[wei], 1);
	return rt;
}

int main(void) {
	scanf("%d%d", &A, &B);
	printf("%d
", slove(B) - slove(A - 1));
	return 0;
}