hdu3555_数位dp

http://acm.hdu.edu.cn/showproblem.php?pid=3555

题意，1-n, 有多少个数含有49

#include <algorithm>
#include <iostream>
#include <cstring>
#include <cstdlib>
#include <cstdio>
#include <vector>
#include <ctime>
#include <queue>
#include <list>
#include <set>
#include <map>
using namespace std;
#define INF 0x3f3f3f3f
typedef long long LL;

LL dp[25][5];
// dp[1][0] = 10;//没有49
// dp[1][1] = 1;//9
// dp[1][2] = 0;//有49
void find()
{
    memset(dp, 0, sizeof(dp));
    dp[0][0] = 1;
    for(int i = 1; i <= 20; i++)
    {
        dp[i][0] = (LL)dp[i - 1][0] * 10 - dp[i - 1][1];
        dp[i][1] = dp[i - 1][0];
        dp[i][2] = (LL)dp[i - 1][2] * 10 + dp[i - 1][1];
    }
}

void solve(LL n)
{
    int len = 0;
    int bit[25];
    while(n)
    {
        bit[++len] = n % 10;
        n /= 10;
    }
    bit[len + 1] = 0;
    LL ans = 0;
    int flag = 0;
    for(int i = len; i > 0; i--)
    {
        ans += (LL)dp[i - 1][2] * bit[i];
        if(flag)
            ans += (LL)dp[i - 1][0] * bit[i];
        if(!flag && bit[i] > 4)
            ans += dp[i - 1][1];
        if(bit[i + 1] == 4 && bit[i] == 9)
            flag = 1;
    }
    printf("%I64d
", ans);
}
int main()
{
    int t;
    LL n;
    scanf("%d", &t);
    find();
    while(t--)
    {
        scanf("%I64d", &n);
        solve(n + 1);
    }
    return 0;
}