AtCoder Regular Contest 080 C - 4-adjacent

地址：http://arc080.contest.atcoder.jp/tasks/arc080_a

题目：

C - 4-adjacent

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Time limit : 2sec / Memory limit : 256MB

Score : 400 points

Problem Statement

We have a sequence of length N, a=(a1,a2,…,aN). Each ai is a positive integer.

Snuke's objective is to permute the element in a so that the following condition is satisfied:

• For each 1≤i≤N−1, the product of ai and ai+1 is a multiple of 4.

Determine whether Snuke can achieve his objective.

Constraints

• 2≤N≤105
• ai is an integer.
• 1≤ai≤109

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Input

Input is given from Standard Input in the following format:

N
a1 a2 … aN

Output

If Snuke can achieve his objective, print Yes; otherwise, print No.

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思路：求膜2为1，膜4为0的数有多少个就好了。

#include <bits/stdc++.h>
 
using namespace std;
 
#define MP make_pair
#define PB push_back
typedef long long LL;
typedef pair<int,int> PII;
const double eps=1e-8;
const double pi=acos(-1.0);
const int K=1e6+7;
const int mod=1e9+7;
 
int n,a,b,c,ans;
 
int main(void)
{
    scanf("%d",&n);
    for(int i=1,x;i<=n;i++)
    {
        scanf("%d",&x);
        if(x%4==0) c++;
        else if(x%2==0) b++;
        else a++;
    }
    c-=a;
    if(c>=0||(c==-1&&b==0)) puts("Yes");
    else    puts("No");
    return 0;
}