C++ String'ten Integer'a

#include <iostream> 
  #include <stdlib.h> 
  using namespace std; 
  int main(){ 
   
  string snot; 
  int inot; 
  cout<<"Bir sayi gir : "; 
  cin>>snot; 
  cout<<endl; 
   
  inot=atoi(snot.c_str());   // string'i integer yapiyor 
   
  inot=inot*5;       // artik istedigin islemi yapabilirsin  
  cout<<inot; 
   
  return 0;}

#include <iostream> 
  #include <string> 
  using namespace std; 
  string ogrencigir; 
  string ogrencinum[4][3]; 
  int a,b; 
  void arama(string) 
  { 
  for(int i=0;i<4;i++) 
  { 
      if(ogrencinum[i][0]==ogrencigir) 
      {a=1; 
      b=i;} 
  } 
  } 
  int main(){ 
   
  for(int x=0;x<4;x++) 
  { 
  cout<<x+1<<". ogrenci adi :"; 
  cin>>ogrencinum[x][0]; 
  cout<<x+1<<". ogrencinin numarasý :"; 
  cin>>ogrencinum[x][1]; 
  cout<<x+1<<". ogrencinin notu :"; 
  cin>>ogrencinum[x][2]; 
  } 
   
   
   
  cout<<"Aranacak ogrenci ismi : "; 
  cin>>ogrencigir; 
  arama(ogrencigir); 
  if(a==1) 
  cout<<ogrencigir<<" adina kayitli bir ogrencimiz wardir\nNumarasi :"<<ogrencinum[b][1]<<"\naldigi not :"<<ogrencinum[b][2]; 
  else 
  {cout<<"kayit yok\n";} 
  return 0; 
  }

#include<iostream> 
  using namespace std; 
   
  struct ogrenci { 
     string adi[3]; 
     string soyadi[3]; 
     int numarasi[3]; 
     int notu[3]; 
  }ogr; 
  int a,b; 
  float ortalama; 
  string araad; 
  void arama(string) 
  { 
  for(int x=0;x<3;x++) 
  { 
      if(ogr.adi[x]==araad) 
      {a=1; 
      b=x;} 
  } 
  } 
  main(){ 
      for(int i=0;i<3;i++) 
      { 
  cout<<i+1<<". Ogrencinin adi: "; 
  cin>>ogr.adi[i]; 
  cout<<i+1<<". Ogrencinin Soyadi: "; 
  cin>>ogr.soyadi[i]; 
  cout<<i+1<<". Ogrencinin okul no: "; 
  cin>>ogr.numarasi[i]; 
  cout<<i+1<<". Ogrencinin notu: "; 
  cin>>ogr.notu[i]; 
      } 
  ortalama=(float)(ogr.notu[0]+ogr.notu[1]+ogr.notu[2])/3; 
  cout<<"Bilgilerini almak istediginiz ogrencinin adini giriniz :"; 
  cin>>araad; 
  arama(araad); 
  if(a==1){ 
  cout<<ogr.numarasi[b]<<" numarali "<<ogr.adi[b]<<ogr.soyadi[b]<<" adli ogrencinin notu: "<<ogr.notu[b]<<endl; 
  cout<<"Ogrencilerin not ortalamasi: "<<ortalama; 
  } 
  else 
  { 
      cout<<"kayit yok!"; 
  } 
  }