delete pics to save space

history_source/挑战程序设计竞赛/2.6.2.2.cpp

@@ -0,0 +1,27 @@
+#include<cstdio>
+#include<cstring>
+int n;
+bool isp[1000005];
+void solve()
+{
+	int p=0,i,j;
+	for(i=2;i<=n;i++)
+		if(isp[i])
+		{
+			p++;
+			for(j=2;j*i<=n;j++) isp[j*i]=0;
+		}
+	printf("%d\n",p);
+}
+void init()
+{
+	scanf("%d",&n);
+	memset(isp,1,sizeof(isp));
+	isp[0]=isp[1]=0;
+}
+int main()
+{
+	init();
+	solve();
+	return 0;
+}