$j$ 为啥 $\leq \sqrt a$。。。$12=5+7$。
by Subset_Sum @ 2024-03-17 16:46:16
?
by youranzide @ 2024-03-17 16:47:21
@[youranzide](/user/1269604)
改成这样。。。
```
#include<bits/stdc++.h>
using namespace std;
bool n(int num){
for(int i=2;i<=sqrt(num);i++){
if (num%i == 0) return false;
}
return true;
}
int main(){
int a;
cin >> a;
for(int i=4;i<=a;i+=2){
for(int j=2;j<=i-2;j++){
if (n(j)&&n(i-j)){
cout << i <<"=" << j << "+" << i-j << endl;
break;
}
}
}
return 0;
}
```
by Subset_Sum @ 2024-03-17 16:49:11
好的谢谢，不过12=5+7是什么意思啊
by youranzide @ 2024-03-17 16:52:49
@[youranzide](/user/1269604) 因为 $\sqrt{12}\le7$ 所以 $j$ 不应该只枚举到 $\sqrt{a}$
by kevinZ99 @ 2024-03-17 17:03:59
@[youranzide](/user/1269604)
根号a改成a/2
```cpp
#include<bits/stdc++.h>
using namespace std;
bool n(int num){
for(int i=2;i<=sqrt(num);i++){
if (num%i == 0) return false;
}
return true;
}
int main(){
int a;
cin >> a;
for(int i=4;i<=a;i+=2){
for(int j=2;j<=a / 2;j++){
if (n(j)&&n(i-j)){
cout << i <<"=" << j << "+" << i-j << endl;
break;
}
}
}
return 0;
}
```
by youcaiyoujuan @ 2024-03-17 20:31:52