qsort problem.

This is a discussion on qsort problem. within the C++ Programming forums, part of the General Programming Boards category; Hello, I have a problem with qsort. I let my program generate 50x40 arrays and after i used qsort. The ...

  1. #1
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    qsort problem.

    Hello,

    I have a problem with qsort. I let my program generate 50x40 arrays and after i used qsort. The result is not 50x40 anymore. It become a

    here is my code
    Code:
    #include <iostream>
    #include <ctime> 
    #include <cstdlib> 
    #include <iomanip>
    using namespace std;
    int compare (const void * a, const void * b)
    {
      return ( *(int*)a - *(int*)b );
    }
    
     
    int main()
    {
        const int row=50;
        const int column=40;
        int table[row][column];
        int rnum;
        int t[row];
     
        srand(time(0)); 
        rnum = (rand() % 100) + 1; 
    
        for(int r=0; r<row; r++)//row
        { 
            for(int c=0; c<column; c++)
                table [r][c] = (rand()%100) + 1;
        }
     
        for(int r=0; r<row; r++)//row
        { 
            for(int c=0; c<column; c++) //column
     
            {
                cout << setw(3) << table[r][c] << ' '; //display table
     
            }
            cout << endl;
        } 
          qsort(table, 50 * 40, sizeof(int), compare);
    
     
        cout << "your new sorted table is: \n";
    
        for(int n=0; n<row; n++)//row
        { 
            for(int m=0; m<column; m++) //column
     
            {
                cout << setw(3) << table[n][m] << ' '; //display table
     
            }
        }
    
    
    
        
     
        
     
            system("pause");
            return 0;
     
    }

  2. #2
    C++ Witch laserlight's Avatar
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    Quote Originally Posted by witt
    I have a problem with qsort.
    Is there any reason why you don't use std::sort?
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  3. #3
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    well I dont even know how to use it or even what it meant sorry

  4. #4
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    std::qsort(table, 5 * 4, sizeof(int), compare); like this?

  5. #5
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    well it still not working
    Last edited by witt; 11-15-2011 at 08:55 PM.

  6. #6
    Algorithm Dissector iMalc's Avatar
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    Since this is C++, forget about qsort. In C++ we use std::sort.
    However, regardless of what you use, you have to understand and convey to us, what it means to be sorting a 2D array.

    And no sorting cannot change the dimensions of an array. Your assumption that this is happening is wrong.
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  7. #7
    Kiss the monkey. CodeMonkey's Avatar
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    You can sort each row, and then sort the columns... or you can define some ordering (zig-zag) and sort it that way. What are you trying to do?
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