BZOJ 1026 [SCOI2009]windy数

Solution

数位DP板子套上就好了

讲解传送门

Code

#include<cstdio>
#include<cstring>
#include<algorithm>
#define rd read()
#define ll long long
using namespace std;

ll sum[15][15];
int a[15];

int read() {
    int X = 0, p = 1; char c = getchar();
    for(; c > '9' || c < '0'; c = getchar()) if(c == '-') p = -1;
    for(; c >= '0' && c <= '9'; c = getchar()) X = X * 10 + c - '0';
    return X * p;
}

int Abs(int x, int y) {
    if(x > y) return x - y;
    else return y - x;
}

ll dfs(int pos, int pre, bool lim, bool lead) {
    if(!pos) return 1;
    if(!lim && !lead && sum[pos][pre] != -1)
        return sum[pos][pre];
    int up = lim ? a[pos] : 9;
    ll tmp = 0;
    for(int i = 0; i <= up; ++i) {
        if(Abs(i , pre) < 2) continue;
        tmp += dfs(pos - 1, (lead && i == 0)? 11 : i, lim && a[pos] == i, lead && i == 0);
    }
    if(!lim && !lead) 
        sum[pos][pre] = tmp;
    return tmp;
}

ll work(int x) {
    int len = 0;
    while(x) {
        a[++len] = x % 10;
        x /= 10;
    }
    return dfs(len, 11, true, true);
}

int main()
{
    int l = rd, r = rd;
    memset(sum, -1, sizeof(sum));
    printf("%lld
", work(r) - work(l - 1));
}