如何使用C ++按字母顺序对3个字符串变量进行排序？

Question

I have 3 strings variables that user enter three words

and must the program sort them alphabetically what I tried to make it with if statement but the problem is if the user insert the first 5 chars are the same I am tired of repeating the code for every time .

Here is my code :

#include <iostream>
using namespace std;
int main ()
{
    string w1,w2,w3;
    cout<<"please enter three words"<<endl;
    cin >> w1 >> w2 >> w3;

    if(w1[0] == w2[0])
    {
        if(w1[1] < w2[1] && w1[0] < w3[0]){
            cout << w1;
            if(w2[0] < w3[0])
            {
                cout << "\t" << w2 <<"\t" << w3;
            }
            else
            {
                cout << "\t" << w3<<"\t" << w2;
            }
        }else if(w2[1] < w1[1] && w2[0] < w3[0]){
            cout << w2;
            if(w1[0] < w3[0])
            {
                cout << "\t" << w1 <<"\t" << w3;
            }
            else
            {
                cout << "\t" << w3<<"\t" << w1;
            }

        }else if(w3[0] < w1[0] && w3[0] < w2[0]){
            cout << w3;
            if(w1[1] < w2[1])
            {
                cout << "\t" << w1 <<"\t" << w2;
            }
            else
            {
                cout << "\t" << w2<<"\t" << w1;
            }

        }
    }
    else if(w2[0] == w3[0])
    {
        if(w1[0] < w2[0] && w1[0] < w3[0]){
            cout << w1;
            if(w2[1] < w3[1])
            {
                cout << "\t" << w2 <<"\t" << w3;
            }
            else
            {
                cout << "\t" << w3<<"\t" << w2;
            }
        }else if(w2[0] < w1[0] && w2[1] < w3[1]){
            cout << w2;
            if(w1[0] < w3[0])
            {
                cout << "\t" << w1 <<"\t" << w3;
            }
            else
            {
                cout << "\t" << w3<<"\t" << w1;
            }

        }else if(w3[0] < w1[0] && w3[1] < w2[1]){
            cout << w3;
            if(w1[0] < w2[0])
            {
                cout << "\t" << w1 <<"\t" << w2;
            }
            else
            {
                cout << "\t" << w2<<"\t" << w1;
            }

        }

    }
    else if(w3[0] == w1[0])
    {
        if(w1[0] < w2[0] && w1[1] < w3[1]){
            cout << w1;
            if(w2[0] < w3[0])
            {
                cout << "\t" << w2 <<"\t" << w3;
            }
            else
            {
                cout << "\t" << w3<<"\t" << w2;
            }
        }else if(w2[0] < w1[0] && w2[0] < w3[0]){
            cout << w2;
            if(w1[1] < w3[1])
            {
                cout << "\t" << w1 <<"\t" << w3;
            }
            else
            {
                cout << "\t" << w3<<"\t" << w1;
            }

        }else if(w3[1] < w1[1] && w3[0] < w2[0]){
            cout << w3;
            if(w1[0] < w2[0])
            {
                cout << "\t" << w1 <<"\t" << w2;
            }
            else
            {
                cout << "\t" << w2<<"\t" << w1;
            }

        }

    }
    else if(w1[0] == w2[0] && w2[0] == w3[0])
    {
        if(w1[1] < w2[1] && w1[1] < w3[1]){
            cout << w1;
            if(w2[1] < w3[1])
            {
                cout << "\t" << w2 <<"\t" << w3;
            }
            else
            {
                cout << "\t" << w3<<"\t" << w2;
            }
        }else if(w2[1] < w1[1] && w2[1] < w3[1]){
            cout << w2;
            if(w1[1] < w3[1])
            {
                cout << "\t" << w1 <<"\t" << w3;
            }
            else
            {
                cout << "\t" << w3<<"\t" << w1;
            }

        }else if(w3[1] < w1[1] && w3[1] < w2[1]){
            cout << w3;
            if(w1[1] < w2[1])
            {
                cout << "\t" << w1 <<"\t" << w2;
            }
            else
            {
                cout << "\t" << w2<<"\t" << w1;
            }

        }
    }
    else if(w1[0] == w2[0] && w2[0] == w3[0] && w1[1] == w2[1] && w2[1] == w3[1])
    {
        if(w1[2] < w2[2] && w1[2] < w3[2]){
            cout << w1;
            if(w2[2] < w3[2])
            {
                cout << "\t" << w2 <<"\t" << w3;
            }
            else
            {
                cout << "\t" << w3<<"\t" << w2;
            }
        }else if(w2[2] < w1[2] && w2[2] < w3[2]){
            cout << w2;
            if(w1[2] < w3[2])
            {
                cout << "\t" << w1 <<"\t" << w3;
            }
            else
            {
                cout << "\t" << w3<<"\t" << w1;
            }

        }else if(w3[2] < w1[2] && w3[2] < w2[2]){
            cout << w3;
            if(w1[2] < w2[2])
            {
                cout << "\t" << w1 <<"\t" << w2;
            }
            else
            {
                cout << "\t" << w2<<"\t" << w1;
            }

        }
    }
    else
    {
        if(w1[0] < w2[0] && w1[0] < w3[0]){
            cout << w1;
            if(w2[0] < w3[0])
            {
                cout << "\t" << w2 <<"\t" << w3;
            }
            else
            {
                cout << "\t" << w3<<"\t" << w2;
            }
        }else if(w2[0] < w1[0] && w2[0] < w3[0]){
            cout << w2;
            if(w1[0] < w3[0])
            {
                cout << "\t" << w1 <<"\t" << w3;
            }
            else
            {
                cout << "\t" << w3<<"\t" << w1;
            }

        }else if(w3[0] < w1[0] && w3[0] < w2[0]){
            cout << w3;
            if(w1[0] < w2[0])
            {
                cout << "\t" << w1 <<"\t" << w2;
            }
            else
            {
                cout << "\t" << w2<<"\t" << w1;
            }

        }
    }
    //cout << w1[0] << "\t" << "\t" <<w2[0] << "\t" << w3[0];
    return 0;
}

If there a way to make this with for loop but with these libraries only

#include <iostream>
#include <stdio.h>
#include <string>
#include <algorithm>

Answer 1

I do not understand what your program tries to do. But take into account that class std::string has relational operators. So there is no need to compare each character individually.

I would write the program the following way:) You may change the program such a way that it would ask the user to enter three strings.

#include <iostream>
#include <string>
#include <functional>
#include <utility>

int main()
{
    std::string s1 = "tom", s2 = "fox", s3 = "hello";
    auto r1 = std::ref( s1 ), r2 = std::ref( s2 ), r3 = std::ref( s3 );

    if ( r2.get() < r1.get() ) std::swap( r1, r2 );
    if ( r3.get() < r2.get() ) std::swap( r2, r3 );
    if ( r2.get() < r1.get() ) std::swap( r1, r2 );

    std::cout << s1<< '\t' << s2 << '\t' << s3 << std::endl;
    std::cout << r1.get() << '\t' << r2.get() << '\t' << r3.get() << std::endl;

    return 0;
}

The output is

tom fox hello
fox hello   tom

Or you can use a straightforward approach

#include <iostream>
#include <string>

int main()
{
    std::string s1 = "tom", s2 = "fox", s3 = "hello";

    if ( s1 <= s2 && s2 <= s3 )
    {
        std::cout << s1<< '\t' << s2 << '\t' << s3 << std::endl;
    }
    else if ( s1 <= s3 && s3 <= s2 )
    {
        std::cout << s1<< '\t' << s3 << '\t' << s2 << std::endl;
    }
    else if ( s2 <= s1 && s1 <= s3 )
    {
        std::cout << s2<< '\t' << s1 << '\t' << s3 << std::endl;
    }
    else if ( s2 <= s3 && s3 <= s1 )
    {
        std::cout << s2<< '\t' << s3 << '\t' << s1 << std::endl;
    }
    else if ( s3 <= s1 && s1 <= s2 )
    {
        std::cout << s3<< '\t' << s1 << '\t' << s2 << std::endl;
    }
    if ( s3 <= s2 && s2 <= s1 )
    {
        std::cout << s3<< '\t' << s2 << '\t' << s1 << std::endl;
    }

    return 0;
}

Answer 2

Try this:

const unsigned int MAX_STRINGS = 3;
string string_container[MAX_STRINGS];
cout<<"please enter three words"<<endl;
cin >> string_container[0]
    >> string_container[1]
    >> string_container[2];
for (unsigned int i = 1; i < MAX_STRINGS; ++i)
{
     if (string_container[i] <= string_container[i - 1])
     {
       std::swap(string_container[i - 1], string_container[i]);
       i = 0;
     }
}

It meets the requirement of having a for loop.

Edit 1: Using std::sort
If you don't need a for loop:

const unsigned int MAX_STRINGS = 3;
string string_container[MAX_STRINGS];
cout<<"please enter three words"<<endl;
cin >> string_container[0]
    >> string_container[1]
    >> string_container[2];
std::sort(&string_container[0], &string_container[MAX_STRINGS];  

Answer 3

int main () {

string list[3];//Array of strings. Makes things easier.
cout<<"please enter three words"<<endl;
cin >> list[0] >> list[1] >> list[2];

//I might be using swap or compare wrong here
//but i guess it it more important that you know these functions exist.
if (list[0].compare(list[1]) < 0) swap(list[0], list[1]);
if (list[0].compare(list[2]) < 0) swap(list[0], list[2]);
if (list[1].compare(list[2]) < 0) swap(list[1], list[2]);

return  0;
}

you can also (and more preferably) use a for loop nested within a for loop as such:

int arraysize = 3;
for (int i = 0 ; i < arraysize ; i++) {
    for (int j = i+1  ; j < arraysize) ; j++) {
        if (list[i].compare(list[j]) < 0) swap(list[i], list[j]);
    }
}

Answer 4

Try this (it's the code from Thomas Matthews, with a simple Bubble Sort )

const unsigned int MAX_STRINGS = 3;
string string_container[MAX_STRINGS];
cout<<"please enter three words"<<endl;
cin >> string_container[0]
    >> string_container[1]
    >> string_container[2];
bool swaped;

do{
   swaped = false;
   for (unsigned int i = 1; i < MAX_STRINGS; ++i)
   {
        if (string_container[i] <= string_container[i - 1])
        {
          std::swap(string_container[i - 1], string_container[i]);
          swaped = true;
        }
   }
}while(swaped);