Member Avatar for nurulshidanoni

Dear all,

I have this code and this data...but i want to sort the sum1 in descending order..but my problem is..i want to sort many array....like this..

after sort
3: ............. 46
1: .............. 25
2:..................20


how to sort in descending order together with the row?


1: 5 6 7 8 29 48 49 68 69 70 73 74 75 76 95 96 103 104 109 110 111 130 132 134 137 25
2: 6 7 29 49 69 70 74 75 95 96 100 103 104 109 110 111 130 132 134 137 20 3: 9 10 11 12 13 14 15 16 30 31 32 33 34 35 36 37 50 51 52 53 54 55 56 57 71 77 78 79 80 81 82 83 84 97 105 106 112 113 114 115 116 117 118 119 135 138 46

#include <iostream>  
#include <fstream>
#include <iomanip>
#include <string>   
#include <vector>    
#include <algorithm> 
using namespace std; 

int g[2000],g1[2000],h[200], s[200];
struct student
{
string studentid;
vector <int> examcode;   
}; 

int myfile;
int main()
{
ifstream stream1 ("STA83STU.txt");
if ( !stream1 )

	{
	cout << "While opening a file an error is encountered" << endl;
	}
	
	else
	{
	cout << "File is  opened" << endl;
	} 		
	vector <student> students;
	student aStudent;
	string tempStudentID;
	bool readEntireFile = false;     
    stream1 >> tempStudentID;   
	while ( !readEntireFile )
{
aStudent.studentid = tempStudentID;  
int tempExamCode;
aStudent.examcode.clear ();
stream1 >> tempExamCode;    
aStudent.examcode.push_back (tempExamCode);  
bool newStudent = false;  
while ( !newStudent && !readEntireFile )
	
	{
	if ( stream1 >> tempStudentID )   
		{
		if ( tempStudentID.compare (aStudent.studentid) == 0 )  
					
			{
			stream1 >> tempExamCode;   
			aStudent.examcode.push_back (tempExamCode); 
			}
				
		else
		newStudent = true;  
		}
				
	else
	readEntireFile = true;  
	}  
	students.push_back (aStudent);   
}
stream1.close ();  
				
{
ofstream myfile;
myfile.open ("212-1.txt");
			
	if (myfile.is_open())
	{
		{
      		{ 
			for (int colHead=1; colHead<140; colHead++)
			cout<<endl;
			int sum, temp,sum1, temp1;
			int count,count2, count3;
			int m, n;
		
			temp=temp1=0;	
    		
				for ( m=1; m<5; m++)
				{  	myfile<<setw(3)<<"\n"<<m<<":";
					for (n=1; n<140; n++)
					{
					count=h[n]=count2=count3=0;
					g1[n]=n;
						for ( int i = 1 ; i < students.size (); i++ )
						{
							for ( int k = 1; k<students.at(i).examcode.size(); k++ )
							{	
								if (students.at(i).examcode.at(0)==m && students.at (i).examcode.at(k)==n)
								{
								count++;
								}
									
								if (students.at(i).examcode.at(0)==n && students.at (i).examcode.at(k)==m)
								{
								count++;
								}	
							}
						}
					g[i]=count;
					sum=g[i]+temp;
					temp=sum;
				
					if(g[i]>=1)
					{
					count2++;
					h[n]=count2;
					}		
					sum1=h[n]+temp1;
					temp1=sum1;

					if(g[i]>=1 )
					{
					myfile<<"\t"<<g1[n];
					}
				  
					}
				
					myfile<<"\t"<<sum1; 
					sum=temp=sum1=temp1=0;
				

					}	
				
			
				
			}	
		}		
	}
return 0;
	}

}
  • 2 Contributors
  • 2 Replies
  • 128 Views
  • 1 Day Discussion Span
  • Latest Post Latest Post by nurulshidanoni

Dani AI

Generated

asked how to sort several rows (each a vector of exam codes) by the number of elements they contain, printing the row label and its count in descending order. pointed out swapping entire rows; a robust, fast way is to use the STL sort with a comparator that compares row sizes instead of writing a bubble sort.

A clear pattern: keep each row together (id + vector) and sort the container of rows. Example approach in C++:

struct Row { int id; std::vector<int> codes; };

std::vector<Row> rows = /* filled from file */;

std::sort(rows.begin(), rows.end(),
          [](const Row &a, const Row &b){
              if (a.codes.size() != b.codes.size())
                  return a.codes.size() > b.codes.size(); // descending
              return a.id < b.id; // tie-breaker: original id order
          });

for (const auto &r : rows) {
    std::cout << r.id << ":";
    for (int x : r.codes) std::cout << '\t' << x;
    std::cout << '\t' << r.codes.size() << '\n';
}

Troubleshooting tips:

  • Use zero-based indices (0 .. size()-1) when iterating vectors. Off-by-one loops are a common source of missing items.
  • If you need to preserve original relative order for equal counts, use std::stable_sort instead of std::sort.
  • For very large datasets prefer std::sort (O(n log n)) over manual bubble sorts (O(n^2)).
  • Add a quick debug print of each row size before sorting to confirm your parser produced the expected counts.

This keeps rows intact, sorts by count in descending order, and prints the row number plus its element count.

Recommended Answers

All 2 Replies

Member Avatar for VernonDozier

Dear all,

I have this code and this data...but i want to sort the sum1 in descending order..but my problem is..i want to sort many array....like this..

after sort
3: ............. 46
1: .............. 25
2:..................20


how to sort in descending order together with the row?


1: 5 6 7 8 29 48 49 68 69 70 73 74 75 76 95 96 103 104 109 110 111 130 132 134 137 25
2: 6 7 29 49 69 70 74 75 95 96 100 103 104 109 110 111 130 132 134 137 20 3: 9 10 11 12 13 14 15 16 30 31 32 33 34 35 36 37 50 51 52 53 54 55 56 57 71 77 78 79 80 81 82 83 84 97 105 106 112 113 114 115 116 117 118 119 135 138 46

The numbers in red are the number of elements in each row. nurulshidanoni, this is something you need to point out. Don't expect people to understand that that is why you highlighted it, particularly since you didn't start row 3 with a new line. I assume each "row" is one student's exam codes? I have no idea what "sum1" refers to. So I'm guessing your question is "How do I sort a vector of integers in descending order?" There are lots of sorts out there. The easiest, in my opinion, is the Bubble Sort:
http://en.wikipedia.org/wiki/Bubble_sort

It then appears that you want to sort entire rows by the number of elements in them in descending order. Bubble sort again, except this time instead of swapping two integers, you are swapping entire rows/vectors.

Member Avatar for nurulshidanoni

Thank you vernon dozier for your great suggestion....

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