Merge pull request ephremdeme#52 from gauravmadan583/master

Optimizing isPrime in C++

Author: ephremdeme

.vscode/launch.json

@@ -0,0 +1,29 @@
+{
+    // Use IntelliSense to learn about possible attributes.
+    // Hover to view descriptions of existing attributes.
+    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
+    "version": "0.2.0",
+    "configurations": [
+        {
+            "name": "g++.exe - Build and debug active file",
+            "type": "cppdbg",
+            "request": "launch",
+            "program": "${fileDirname}\\${fileBasenameNoExtension}.exe",
+            "args": [],
+            "stopAtEntry": false,
+            "cwd": "${workspaceFolder}",
+            "environment": [],
+            "externalConsole": false,
+            "MIMode": "gdb",
+            "miDebuggerPath": "C:\\MinGW\\bin\\gdb.exe",
+            "setupCommands": [
+                {
+                    "description": "Enable pretty-printing for gdb",
+                    "text": "-enable-pretty-printing",
+                    "ignoreFailures": true
+                }
+            ],
+            "preLaunchTask": "C/C++: g++.exe build active file"
+        }
+    ]
+}

.vscode/tasks.json

@@ -0,0 +1,26 @@
+{
+    "tasks": [
+        {
+            "type": "shell",
+            "label": "C/C++: g++.exe build active file",
+            "command": "C:\\MinGW\\bin\\g++.exe",
+            "args": [
+                "-g",
+                "${file}",
+                "-o",
+                "${fileDirname}\\${fileBasenameNoExtension}.exe"
+            ],
+            "options": {
+                "cwd": "${workspaceFolder}"
+            },
+            "problemMatcher": [
+                "$gcc"
+            ],
+            "group": {
+                "kind": "build",
+                "isDefault": true
+            }
+        }
+    ],
+    "version": "2.0.0"
+}

problems/isPrime.cpp

@@ -3,21 +3,29 @@ using namespace std;
 
 int main()
 {
+    ios_base::sync_with_stdio(false);
+    cin.tie(NULL);
+    cout.tie(NULL);
+
     int n;
     cin>>n;
-    int d=2;
     bool divided=false;
-    while(d<n)
-    {
-        if(n%d==0)
-        {
-            cout<<"False"<<endl;
-            divided=true;
+    if(n%2==0){
+        divided=true;
+    }
+    else{
+        int d=3;
+        while(d*d<n){
+            if(n%d==0){
+                divided=true;
+                break;
+            }
+            d+=2;
         }
-        d++;
     }
-    if(!divided)
-    {
+    if(!divided){
         cout<<"True"<<endl;
+    }else{
+        cout<<"False"<<endl;
     }
 }