poj 3286 How many 0's? --- 数位dp

找找规律就可以

#include <iostream>#include <cstring>#include <string>#include <cstdio>#include <cmath>#include <algorithm>#include <vector>#include <queue>#include <map>#define inf 0x3f3f3f3f#define ll __int64using namespace std;ll a[12]={1LL,10LL,100LL,1000LL,10000LL,100000LL,1000000LL,10000000LL,100000000LL,1000000000LL,10000000000LL,100000000000LL};ll cal(ll n){    ll ans=0,left,tmp;    for(int i=1;i<12;i++)    {        left=n/a[i]-1;        ans+=left*a[i-1];        tmp=(n%a[i]-n%a[i-1])/a[i-1];        if(tmp>0) ans+=a[i-1];        else if(tmp==0) ans+=n%a[i-1]+1;        if(n<a[i]) break;    }    return ans;}int main(){    ll n,m;    while(scanf("%I64d%I64d",&n,&m)&&m>=0)    {        printf("%I64d\n",cal(m)-cal(n-1));    }    return 0;}