Sorting a list

[Uber Meister]

I have a .txt file which I want to read from and then write a new text file, this time with sorted lines. It is easy to sort one value, but what about sorting entire lines based on one value?

I want to sort the lines based on the FIRST value.

Example text file contents:

values;data
5.01 100
2.9 342
2.69 43534
10.1 43
6.8 45324

Output: Text file containing

2.69 43534
2.9 342
5.01 100
6.8 45324
10.1 43

It's easy to do this if there was only 1 number on each line, but I do I sort all the lines based on the first number in each line?

[dhayden]

If this is a unix system, just do sort -n < file.txt

If you have to write the code, then you need a class with two members: the number and the string. Add operator < that works on the number. Now read the files, populate an instance of your class and drop it into a std::set. When you're done, just iterate over the set and write them out. This will work because sets are ordered.

[Chervil]

What if there are duplicate lines, (or duplicate first values), the std::set will omit duplicates, won't it?

However, there is a std::sort which can work with a std::vector, might be better to use that than a set.