【数位DP】 HDU 4722 Good Numbers

原题直通车: HDU  4722  Good Numbers

题意: 求区间[a,b]中各位数和mod 10==0的个数.

代码:

#include<iostream>#include<cstdio>#include<cstring>#include<cmath>using namespace std;int f[20];long long work(long long x){    long long ret=0, u=x;    int t=0, s=0;    while(u) f[++t]=u%10, u/=10;    for(int i=t; i>=1; --i){        if(i==1){            for(int j=0; j<f[i]; ++j)                if((s+j)%10==0) ret++;            break;        }        for(int j=0; j<f[i]; ++j)            ret+=(long long) pow(10.0, i-2);        s=(s+f[i])%10;    }    return ret;}int main(){    int T, cas=1; scanf("%d",&T);    while(T--){        long long a, b;        scanf("%I64d%I64d", &a, &b);        printf("Case #%d: %I64d\n", cas++, work(b+1)-work(a));    }    return 0;}