标签：hdu 3555 bomb   数位dp   

Bomb

3
1
50
500

0
1
15

Hint
From 1 to 500, the numbers that include the sub-sequence "49" are "49","149","249","349","449","490","491","492","493","494","495","496","497","498","499",
so the answer is 15.
 

含49的个数。

#include<cstdio>
#include<algorithm>
#include<cstring>
#include<iostream>
#include<cmath>
#define N 1010
#define ll long long

using namespace std;

ll dp[30][3];//0:合法  1:9开头  2：不合法 
             ///dp[i][j]  长度为i的j状态

void init() {
    memset(dp,0,sizeof dp);
    dp[0][2]=1;
    for(int i=1; i<=24; i++) {
        dp[i][0]=dp[i-1][0]*10+dp[i-1][1];
        dp[i][1]=dp[i-1][2];
        dp[i][2]=dp[i-1][2]*10-dp[i-1][1];
    }
}

ll solve(ll n) {
    int a[40];
    int len=1;
    while(n) {
        a[len++]=n%10;
        n/=10;
    }
    a[len]=0;
    ll ans=0;
    int flag=0;
    for(int i=len-1; i>=1; i--) {
        ans+=dp[i-1][0]*a[i];
        if(flag)
            ans+=dp[i-1][2]*a[i];
        if(!flag&&a[i]>4)
            ans+=dp[i-1][1];
        if(a[i]==9&&a[i+1]==4)  ///xx49***的情况  *为待填数位
            flag=1;
    }
    return ans;
}

int main() {
    init();
    int t;
    cin>>t;
    while(t--) {
        ll n;
        cin>>n;
        printf("%I64d\n",solve(n+1));
    }
    return 0;
}

hdu 3555 Bomb（数位dp）

标签：hdu 3555 bomb   数位dp   

原文地址：http://blog.csdn.net/acm_baihuzi/article/details/45223707