sort question

Code:

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#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
using namespace std;
int main()
{
  std::vector<string> vec;
  vec.push_back("dd"); vec.push_back("adfd"); vec.push_back("aaa");
  vec.push_back("aa");
  std::sort(vec.begin(), vec.end());
  for (int i = 0; i < vec.size(); ++i)
    std::cout << vec[i] << ' ';
}

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I want to output
aa
dd
aaa
adfd


How to design codes?

What does that code output now?

You should write a custom comparator that takes the length of the strings being compared into consideration.

Quote:

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Originally Posted by MutantJohn

What does that code output now?

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aa aaa adfd dd

Have you tried my suggestion?

Quote:

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Originally Posted by zcrself

aa aaa adfd dd

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Ah, I see. Then you should without a doubt follow laserlight's advice and use a custom comparator that incorporates string length. I think std::sort() actually has an implementation of this, doesn't it? It's something with an argument list like std::sort(iterator & A, iterator & B, comparison_function), isn't it? That way you can sort by string length as well.

Yes, it has an overloaded function that takes a comparator as a 3rd argument.
std::sort - cppreference.com
The other alternative would be to overload operator < for the type you're trying to sort (unless it's a built-in such as int, std::string, etc).

Quote:

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Originally Posted by laserlight

Have you tried my suggestion?

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I do appreciate your suggestion, thanks a lot

Code:

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bool cmp1(string a, string b)
{
    if(a.length()==b.length())
    {
        return a < b;
    }else
    {
        return a.length() < b.length();
    }
}

std::sort(vec.begin(), vec.end(),cmp1);

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Quote:

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Originally Posted by Elysia

Yes, it has an overloaded function that takes a comparator as a 3rd argument.
std::sort - cppreference.com
The other alternative would be to overload operator < for the type you're trying to sort (unless it's a built-in such as int, std::string, etc).

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thanks for your suggestion!

More succinctly put, this seems to work:

return a.length() <= b.length() && a < b;

Quote:

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Originally Posted by whiteflags

More succinctly put, this seems to work:

return a.length() <= b.length() && a < b;

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Assuming an ASCII-based character set, zcrself's code will return true for cmp1("b", "ab"). Your expression will evaluate to false instead. Furthermore, your expression will also evaluate to false for cmp1("ab", "b"), i.e., it indicates that "b" and "ab" are equal according to your comparator.

Quote:

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Originally Posted by whiteflags

More succinctly put, this seems to work:

return a.length() <= b.length() && a < b;

---

Code:

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bool cmp1(string a, string b)
{
    return a.length() <= b.length() && a < b;
}
int main()
{
  std::vector<string> vec;
  vec.push_back("ab"); vec.push_back("b"); vec.push_back("aaa");
  vec.push_back("aa");
  std::sort(vec.begin(), vec.end(),cmp1);
  for (int i = 0; i < vec.size(); ++i)
    std::cout << vec[i] << ' ';
}

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output is:

Code:

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aa ab b aaa

---

Quote:

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Originally Posted by zcrself

output is:

Code:

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aa ab b aaa

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I think the output is supposed to be

Code:

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b aa ab aaa

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which what zcrself's version does.

Quote:

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Originally Posted by rcgldr

I think the output is supposed to be

Code:

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b aa ab aaa

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which what zcrself's version does.

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Code:

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Dev-c++ 4.9.9.2

windows xp

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