[問題] 新手寫的判斷質數程式
剛自學不到一個禮拜，想了很久才寫出這個習題，
自己測試大致上是 OK，不過還是想請教大家幾個問題。
程式如下：
#include <iostream>
#include <math.h>
using namespace std;
int main()
{
int x,y;
printf("質數判別小程式\n\n");
printf("請輸入一個正整數:");
scanf("%d",&x);
if(x==1)
{
cout<<"1 不是質數"<<endl;
}
if(x==2)
{
cout<<"2 是質數"<<endl;
}
for(y=2;y<x;y++)
{
if(x%y==0)
{
cout<<x<<"非質數"<<endl;
break;
}
if(x%y!=0&&(y+1)==x)
cout<<x<<"乃質數"<<endl;
}
system("pause");
}
想請問大家這樣寫 OK 嗎？ (有沒有甚麼地方多餘或是有邏輯盲點的？)
自己測試好像OK，不過輸入的數字太大就不會判斷是否質數了，why，@@?
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