AtCoder Beginner Contest 069

C - 4-adjacent

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:

Na1 a2 … aN

Output

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

Sample Input 1

31 10 100

Sample Output 1

Yes

One solution is (1,100,10).

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Sample Input 2

41 2 3 4

Sample Output 2

No

It is impossible to permute a so that the condition is satisfied.

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Sample Input 3

31 4 1

Sample Output 3

Yes

The condition is already satisfied initially.

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Sample Input 4

21 1

Sample Output 4

No

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Sample Input 5

62 7 1 8 2 8

Sample Output 5

Yes

yes的条件：总数的一半要 <= 被4整除数的个数  | |  被4整除数的个数*2+被2整除但不能被4整除数的个数 <= 总数。

#include <iostream>  #include <cstring>  #include <algorithm>  using namespace std;  int a[100005];  int main()  {      int n,f=0,i,x=0,y=0;      while(cin>>n)      {          for(i=0;i<n;i++)          {              cin>>a[i];          }                for(i=0;i<n;i++)              {                   if(a[i]%4==0)x++;                   if(a[i]%2==0&&a[i]%4!=0)y++;                   if(x*2+y>=n||x>=n/2)                   f=1;              }                 if(f)cout<<"Yes"<<endl;              else cout<<"No"<<endl;      }      return 0;  }