地址:
题目:
You are given several queries. In the i-th query you are given a single positive integer ni. You are to represent ni as a sum of maximum possible number of composite summands and print this maximum number, or print -1, if there are no such splittings.
An integer greater than 1 is composite, if it is not prime, i.e. if it has positive divisors not equal to 1 and the integer itself.
The first line contains single integer q (1 ≤ q ≤ 105) — the number of queries.
q lines follow. The (i + 1)-th line contains single integer ni (1 ≤ ni ≤ 109) — the i-th query.
For each query print the maximum possible number of summands in a valid splitting to composite summands, or -1, if there are no such splittings.
1
12
3
2
6
8
1
2
3
1
2
3
-1
-1
-1
12 = 4 + 4 + 4 = 4 + 8 = 6 + 6 = 12, but the first splitting has the maximum possible number of summands.
8 = 4 + 4, 6 can't be split into several composite summands.
1, 2, 3 are less than any composite number, so they do not have valid splittings.
思路:
最小合数是4,所以用4去凑就行了
1 #include <bits/stdc++.h> 2 3 using namespace std; 4 5 #define MP make_pair 6 #define PB push_back 7 typedef long long LL; 8 typedef pair<int,int> PII; 9 const double eps=1e-8; 10 const double pi=acos(-1.0); 11 const int K=1e6+7; 12 const int mod=1e9+7; 13 14 15 int main(void) 16 { 17 int n,x,ans;cin>>x; 18 while(x--) 19 { 20 scanf("%d",&n); 21 if(n%4==0) 22 ans=n/4; 23 else if(n%4==1) 24 { 25 if(n<9) 26 ans=-1; 27 else if(n==9) 28 ans=1; 29 else 30 ans=(n-13)/4+2; 31 } 32 else if(n%4==2) 33 { 34 if(n<6) 35 ans=-1; 36 else if(n==6) 37 ans=1; 38 else 39 ans=n/4; 40 } 41 else 42 { 43 if(n<15) 44 ans=-1; 45 else 46 ans=(n-15)/4+2; 47 } 48 printf("%d ",ans); 49 } 50 return 0; 51 }