1 second
256 megabytes
standard input
standard output
One way to create a task is to learn from math. You can generate some random math statement or modify some theorems to get something new and build a new task from that.
For example, there is a statement called the "Goldbach's conjecture". It says: "each even number no less than four can be expressed as the sum of two primes". Let's modify it. How about a statement like that: "each integer no less than 12 can be expressed as
the sum of two composite numbers." Not like the Goldbach's conjecture, I can prove this theorem.
You are given an integer n no less than 12, express it as a sum of two composite numbers.
The only line contains an integer n (12 ≤ n ≤ 106).
Output two composite integers x and y (1 < x, y < n) such
that x + y = n. If there are multiple solutions, you can output any of them.
12
4 8
15
6 9
23
8 15
1000000
500000 500000
In the first example, 12 = 4 + 8 and both 4, 8 are composite numbers. You can output "6 6" or "8 4" as well.
In the second example, 15 = 6 + 9. Note that you can't output "1 14" because 1 is not a composite number.
题解
模拟即可。
PS：第一次参加7题3小时的比赛，顿感手速慢的痛苦。
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<iostream>
#include<cmath>
#include<algorithm>
using namespace std;
int n;
bool check(int x)
{
int i;
for(i=2;i<=sqrt(x);i++)
{if(x%i==0) return true;}
return false;
}
int main()
{
scanf("%d",&n);
int i;
for(i=2;i<=n/2;i++)
{if(check(i)&&check(n-i))
{printf("%d %d\n",i,n-i); return 0;}
}
return 0;
}