题目传送门：http://acm.hdu.edu.cn/showproblem.php?pid=2089
还是数位dp
#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
const int MAXN = 10;
int f[MAXN][MAXN];
inline void prework(){
for (int i=0;i<=9;i++) f[1][i] = (i != 4);
for (int k=2;k<=6;k++) {
for (int i=0;i<=9;i++) {
if (i == 4) continue;
else for (int j=0;j<=9;j++)
if (i == 6 && j == 2) continue;
else f[k][i] += f[k-1][j];
}
}
}
inline int cal(int w){
if (!w) return 0;
int ret=0,tot=0,arr[MAXN];
memset(arr,0,sizeof(arr));
while (w) arr[++tot] = w % 10, w /= 10;
for (int i=tot-1;i;i--) for (int j=1;j<=9;j++) ret += f[i][j];
for (int i=tot;i;i--) {
for (int j=(i==tot?1:0);j<arr[i];j++)
if (arr[i+1] == 6 && j == 2) continue;
else ret += f[i][j];
if ((arr[i] == 2 && arr[i+1] == 6) || arr[i] == 4) break;
else if (i == 1) ret ++;
}
return ret;
}
int main(){
prework(); int a,b;
while (scanf("%d%d",&a,&b) && (a || b))
printf("%d\n",cal(b)-cal(a-1));
return 0;
}
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