Code Forces 698A Vacations

题目描述

Vasya has nn days of vacations! So he decided to improve his IT skills and do sport. Vasya knows the following information about each of this nn days: whether that gym opened and whether a contest was carried out in the Internet on that day. For the ii -th day there are four options:

1. on this day the gym is closed and the contest is not carried out;
2. on this day the gym is closed and the contest is carried out;
3. on this day the gym is open and the contest is not carried out;
4. on this day the gym is open and the contest is carried out.

On each of days Vasya can either have a rest or write the contest (if it is carried out on this day), or do sport (if the gym is open on this day).

Find the minimum number of days on which Vasya will have a rest (it means, he will not do sport and write the contest at the same time). The only limitation that Vasya has — he does not want to do the same activity on two consecutive days: it means, he will not do sport on two consecutive days, and write the contest on two consecutive days.

It is an easy DP but has a long DP funcation.

0 means rest, 1 means contest and 2 means sport.

Then the DP funcation come up quickly (i-1 means the last day):

if(day[i]==0) dp[i][0]=min(dp[i-1][0],min(dp[i-1][1],dp[i-1][2]))+1;
if(day[i]==1) dp[i][0]=min(dp[i-1][0],min(dp[i-1][1],dp[i-1][2]))+1,dp[i][2]=min(dp[i-1][0],dp[i-1][1]);
if(day[i]==2) dp[i][0]=min(dp[i-1][0],min(dp[i-1][1],dp[i-1][2]))+1,dp[i][1]=min(dp[i-1][0],dp[i-1][2]);
if(day[i]==3) dp[i][0]=min(dp[i-1][0],min(dp[i-1][1],dp[i-1][2]))+1,dp[i][2]=min(dp[i-1][0],dp[i-1][1]),dp[i][1]=min(dp[i-1][0],dp[i-1][2]);

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#define in(a) a=read()
#define REP(i,k,n)  for(int i=k;i<=n;i++) 
using namespace std;
inline int read(){
    int x=0,f=1;
    char ch=getchar();
    for(;!isdigit(ch);ch=getchar())
        if(ch=='-')
            f=-1;
    for(;isdigit(ch);ch=getchar())
        x=x*10+ch-'0';
    return x*f;
}
int n,m;
int day[1010],dp[1010][3]; 
int main(){
    in(n);
    memset(dp,127,sizeof(dp)); 
    REP(i,1,n)  in(day[i]);
    dp[0][0]=dp[0][1]=dp[0][2]=0; 
    REP(i,1,n){
        if(day[i]==0)  dp[i][0]=min(dp[i-1][0],min(dp[i-1][1],dp[i-1][2]))+1;
        if(day[i]==1)  dp[i][0]=min(dp[i-1][0],min(dp[i-1][1],dp[i-1][2]))+1,dp[i][2]=min(dp[i-1][0],dp[i-1][1]);
        if(day[i]==2)  dp[i][0]=min(dp[i-1][0],min(dp[i-1][1],dp[i-1][2]))+1,dp[i][1]=min(dp[i-1][0],dp[i-1][2]);
        if(day[i]==3)  dp[i][0]=min(dp[i-1][0],min(dp[i-1][1],dp[i-1][2]))+1,dp[i][2]=min(dp[i-1][0],dp[i-1][1]),dp[i][1]=min(dp[i-1][0],dp[i-1][2]);
        //cout<<dp[i][0]<<" "<<dp[i][1]<<" "<<dp[i][2]<<endl; 
    }
    cout<<min(dp[n][0],min(dp[n][1],dp[n][2])); 
    return 0;
}