Codeforces Round #363 (Div. 2) C. Vacations

C. Vacations

time limit per test

1 second

memory limit per test

256 megabytes

input

standard input

output

standard output

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

Input

The first line contains a positive integer n (1 ≤ n ≤ 100) — the number of days of Vasya's vacations.

The second line contains the sequence of integers a1, a2, ..., an (0 ≤ ai ≤ 3) separated by space, where:

• ai equals 0, if on the i-th day of vacations the gym is closed and the contest is not carried out;
• ai equals 1, if on the i-th day of vacations the gym is closed, but the contest is carried out;
• ai equals 2, if on the i-th day of vacations the gym is open and the contest is not carried out;
• ai equals 3, if on the i-th day of vacations the gym is open and the contest is carried out.

Output

Print the minimum possible number of days on which Vasya will have a rest. Remember that Vasya refuses:

• to do sport on any two consecutive days,
• to write the contest on any two consecutive days.

Examples

input

4
1 3 2 0

output

2

input

7
1 3 3 2 1 2 3

output

0

input

2
2 2

output

1

题意：

给出n个数，0表示这天休息，1表示做比赛，2表示运动，3既比赛又运动

问每天只能做一件事，相邻两天不能坐同一件事 n天最少能休息多少天

 

参考大牛的代码  果然透彻

dp[i][0] 第i天休息 前i天能得到的最少休息天数

dp[i][1] 第i天比赛 前i天能得到的最少休息天数

dp[i][2] 第i天运动 前i天能得到的最少休息天数

 

那么

dp[i][1]=min(dp[i-1][0],dp[i-1][2]) 

dp[i][2]=min(dp[i-1][0],dp[i-1][1]) 

dp[i][0]=min(dp[i-1][0],dp[i-1][1],dp[i-1][2])+1 

 

/* ***********************************************
Author        :guanjun
Created Time  :2016/7/22 20:16:52
File Name     :cf363c.cpp
************************************************ */
#include <iostream>
#include <cstring>
#include <cstdlib>
#include <stdio.h>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <string>
#include <math.h>
#include <stdlib.h>
#include <iomanip>
#include <list>
#include <deque>
#include <stack>
#define ull unsigned long long
#define ll long long
#define mod 90001
#define INF 0x3f3f3f3f
#define maxn 10010
#define cle(a) memset(a,0,sizeof(a))
const ull inf = 1LL << 61;
const double eps=1e-5;
using namespace std;
priority_queue<int,vector<int>,greater<int> >pq;
struct Node{
    int x,y;
};
struct cmp{
    bool operator()(Node a,Node b){
        if(a.x==b.x) return a.y> b.y;
        return a.x>b.x;
    }
};

bool cmp(int a,int b){
    return a>b;
}
int a[110];
int dp[110][4];
int main()
{
    #ifndef ONLINE_JUDGE
    freopen("in.txt","r",stdin);
    #endif
    //freopen("out.txt","w",stdout);
    int n;
    cin>>n;
    for(int i=1;i<=n;i++)cin>>a[i];
    for(int i=1;i<=n;i++){
        dp[i][0]=min(dp[i-1][0],min(dp[i-1][1],dp[i-1][2]))+1;//因为每天都可以选择休息
        if(a[i]==1||a[i]==3)dp[i][1]=min(dp[i-1][0],dp[i-1][2]);
        else dp[i][1]=INF;
        if(a[i]==2||a[i]==3)dp[i][2]=min(dp[i-1][0],dp[i-1][1]);
        else dp[i][2]=INF;
    }
    printf("%d\n",min(dp[n][0],min(dp[n][1],dp[n][2])));
    return 0;
}