Linear Search not working properly

lebronjames (21)
I have programmed my linear search to find/display student records. However, I have noticed that there is an error in my program. The problem is that whatever value I enter for the student ID, it will always display "record does not exist". Even if I type in an valid id (such as "P1001"), it still displays "record does not exist".
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#include <iostream>
#include <string>
using namespace std;

struct StudentRecord
{
       string studentID;
       float studentMark;
       char studentGrade;
} student;

int i;
int totalStudents;
int linearSearch (StudentRecord*students,const string studentID);

int main()
{
    int menu;
    StudentRecord student[] = {
                  {"P1001",78.50,'D'},
                  {"P1002",66,'C'}
                  };
    int totalStudents=2;
    float totalMarks=0;
    float averageMark;
    string id;
    int mark;
    int j;
    int found = linearSearch(student,id);
    
    cout << "MAIN MENU\n"
         << "0. Exit         1. Statistics\n"
         << "2. Enter mark   3. Find mark\n"
         << "------------------------------\n"
         << "Your choice -> ";
    cin >> menu;
  while (menu != 0)
  {
    switch (menu)
    {
           case 1:
                for(int j=0;j<totalStudents;j++)
                 {
                   totalMarks+=student[j].studentMark;
                 }
                 averageMark=totalMarks/totalStudents;
                 cout << "Number of records: " << totalStudents <<endl;
                 cout << "Mean or average: " << averageMark <<endl;
                break;
           case 2:
                cout << "Enter a Student Record: " <<endl;
                cout << "Student ID -> ";
                cin >> id;
                  cout << "Student ID already exists" << endl;
                 
                break;
           case 3:
                cout << "Find marks for ID -> ";
                cin >> id;
                if(found!=-1)
                {
                  cout << "-------------" << endl;
                  cout << "Student ID: " << student[found].studentID << endl;
                  cout << "Mark/Grade: " << student[found].studentMark << " (" << student[found].studentGrade << ")" << endl;
                  cout << "-------------" << endl;
                }
                else
                  cout << "Record does not exist" << endl;

                break;
           default:
                   cout << "Invalid selection. Please make a selection between 0-3.\n"
                        << endl;
                   break;
    }    
system("Pause");
    cout << "MAIN MENU\n"
         << "0. Exit         1. Statistics\n"
         << "2. Enter mark   3. Find mark\n"
         << "----------------------------\n"
         << "Your choice -> ";
    cin >> menu;
  }
 
return 0;
}

int linearSearch(StudentRecord*students,const string studentID)

{
    int retValue(-1);
    for(int i=0;i<totalStudents;++i)
    {
            if(students[i].studentID == studentID)
            {
              retValue=i;
              break;
            }
    }
    return retValue;
}


Anybody have any suggestions?
helios (17607)
You call linearSearch() on line 29 but input id on line 59.
lebronjames (21)
I have re-arranged the coding as follows:

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#include <iostream>
#include <string>
using namespace std;

struct StudentRecord
{
       string studentID;
       float studentMark;
       char studentGrade;
} student;

int i;
int totalStudents;
int linearSearch (StudentRecord*students,const string id);

int main()
{
    int menu;
    StudentRecord student[] = {
                  {"P1001",78.50,'D'},
                  {"P1002",66,'C'}
                  };
    int totalStudents=2;
    float totalMarks=0;
    float averageMark;
    string id;
    int mark;
    int j;
    
    cout << "MAIN MENU\n"
         << "0. Exit         1. Statistics\n"
         << "2. Enter mark   3. Find mark\n"
         << "------------------------------\n"
         << "Your choice -> ";
    cin >> menu;
  while (menu != 0)
  {
    switch (menu)
    {
           case 1:
                for(int j=0;j<totalStudents;j++)
                 {
                   totalMarks+=student[j].studentMark;
                 }
                 averageMark=totalMarks/totalStudents;
                 cout << "Number of records: " << totalStudents <<endl;
                 cout << "Mean or average: " << averageMark <<endl;
                break;
           case 2:
                cout << "Enter a Student Record: " <<endl;
                cout << "Student ID -> ";
                cin >> id;
                  cout << "Student ID already exists" << endl;
                 
                break;
           case 3:
                cout << "Find marks for ID -> ";
                cin >> id;
                int found = linearSearch(student,id);
                if(found!=-1)
                {
                  cout << "-------------" << endl;
                  cout << "Student ID: " << student[found].studentID << endl;
                  cout << "Mark/Grade: " << student[found].studentMark << " (" << student[found].studentGrade << ")" << endl;
                  cout << "-------------" << endl;
                }
                else
                  cout << "Record does not exist" << endl;
                  
                break;
           default:
                   cout << "Invalid selection. Please make a selection between 0-3.\n"
                        << endl;
                   break;
    }    
system("Pause");
    cout << "MAIN MENU\n"
         << "0. Exit         1. Statistics\n"
         << "2. Enter mark   3. Find mark\n"
         << "----------------------------\n"
         << "Your choice -> ";
    cin >> menu;
  }
 
return 0;
}

int linearSearch(StudentRecord*students,const string id)

{
    int retValue(-1);
    for(int i=0;i<totalStudents;++i)
    {
            if(students[i].studentID == id)
            {
              retValue=i;
              break;
            }
    }
    return retValue;
}


But i still get the following errors:
- In function `int main()':
- 71 jump to case label
- 59 crosses initialization of `int found'

How can I fix these errors?
helios (17607)
That's what happens when you declare variables inside a switch case. When you need to do that, just surround the case with {}.
For example:
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case 1:
    {
        int a=0;
    }
    break;
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