delete pics to save space

history_source/ccf 基础篇/U7/7.6.4.cpp

@@ -0,0 +1,48 @@
+#include<cstdio>
+#include<cstdlib>
+#define MAXN 550
+#define MAX MAXN/2-1
+using namespace std;
+bool isp[MAXN],use[MAX+1];
+int ans[MAX];
+int x;
+void search(int n)
+{
+	if(n==x) 
+	{
+		if(isp[ans[x-1]+ans[0]])
+		{
+			for(int i=0;i<x;i++) printf("%d ",ans[i]);
+			exit(0);
+		}
+	}
+	for(int i=1;i<=x;i++)
+	{
+		if((!use[i])&&isp[ans[n-1]+i])
+		{
+			use[i]=1;
+			ans[n]=i;
+			search(n+1);
+			use[i]=0;
+		}
+	}
+}
+int main()
+{
+	for(int i=2;i<MAXN;i++) isp[i]=1;
+	for(int i=2;i<MAXN;i++)
+		if(isp[i])
+			for(int j=2;j*i<MAXN;j++)
+				isp[j*i]=0;
+//	scanf("%d",&x);
+	x=20;
+	if(x&1)
+	{
+		printf("-1\n");
+		return 0;
+	}
+	use[1]=1;
+	ans[0]=1;
+	search(1);
+	return 0;
+}