素数密度（循环用sqrt）

3069_includesushu/new4.24(ture).cpp

@@ -0,0 +1,45 @@
+#include <algorithm>
+#include <iostream>
+#include <math.h>
+using namespace std;
+bool pan[10000001] = { 0 };
+int su[100001] = { 0 };
+bool zhi[100001] = { 0 };
+int main()
+{
+    int begn, ends;
+    int now = 0;
+    cin >> begn >> ends;
+    if(begn<2){
+        begn=2;
+    }
+    //cout << begn << ";" << ends << endl;
+    int len = sqrt(ends);
+    for (int i = 2; i <= len; i++) {
+        //cout << i << "/";
+        if (zhi[i] == 0) {
+            su[++now] = i;
+        }
+        for (int j = 1; j <= now && i * su[j]<= len; j++) {
+            zhi[i * su[j]] = 1;
+            if (i % su[j] == 0) {
+                break;
+            }
+        }
+    }
+    for (int u = 1; u <= now; u++) {
+        int i = su[u];
+        //cout << i << " ";
+        for (int j = ends / i; i * j >= begn && j != 1; j--) {
+            pan[i * j - begn] = 1;
+        }
+    }
+    int ans = 0;
+    for (int i = 0; i <= ends - begn; i++) {
+        if (pan[i] == 0) {
+            ans++;
+            //cout<<begn+i<<" ";
+        }
+    }
+    cout << ans;
+}

3069_includesushu/new4.24.cpp

@@ -1,22 +0,0 @@
-#include <iostream>
-#include <algorithm>
-using namespace std;
-bool pan[1000001]={0};
-int main()
-{
-    int begn, ends;
-    cin >> begn >> ends;
-    for (int i = 2; i * i <= ends; i++) {
-        for(int j=ends/i;i*j>=begn&&j!=1;j--){
-            pan[i*j-begn]=1;
-        }
-    }
-    int ans=0;
-    for(int i=0;i<=ends-begn;i++){
-        if(pan[i]==0){
-            ans++;
-            //cout<<begn+i<<" ";
-        }
-    }
-    cout<<ans;
-}

3069_includesushu/test/in.txt

@@ -1 +1 @@
-2 11
+2146483647 2147483647

3069_includesushu/test/out.txt

@@ -1,18 +1,18 @@
 ## z:\Chao\src\3069_includesushu\test\in.txt 
-2020/04/24 周五 18:49:17.02 
-5
+2020/04/27 周一 11:21:02.03 
+46603
 -----------------------------------------------
-Process exited after 160 ms with return value 0
+Process exited after 180 ms with return value 0
 
 ## z:\Chao\src\3069_includesushu\test\in2.txt 
-2020/04/24 周五 18:49:17.02 
-69
+2020/04/27 周一 11:21:02.03 
+664579
+-----------------------------------------------
+Process exited after 420 ms with return value 0
+
+## z:\Chao\src\3069_includesushu\test\in3.txt 
+2020/04/27 周一 11:21:02.03 
+0
 -----------------------------------------------
 Process exited after 80 ms with return value 0
 
-## z:\Chao\src\3069_includesushu\test\in3.txt 
-2020/04/24 周五 18:49:17.02 
-705
------------------------------------------------
-Process exited after 90 ms with return value 0
-