C++ arrays中的排序数字

Question

I am trying to get this out put:

• 1 10
• 2 9
• 3 8
• 4 7
• 5 6

How do I do that?

My code:

 #include <iostream>
    #include <cmath>
    
    using namespace std;
    
    int main()
    {
        const int n=10;
        int Tab[n]={1,2,3,4,5,6,7,8,9,10};
    
    
        for(int i=0; i<5; i++)
            for(int j=5; j>=0; j--)
                cout << Tab[i] << " " << Tab[j] << endl;
    
    
        return 0;
    }

Answer 1

How do I do that?

You do not need 2 loops, you just use one loop and calculate second index:

    for(int i=0; i<n/2; i++) 
        cout << Tab[i] << " " << Tab[n-i-1] << endl;

Live example

PS in this form for array with odd number of elements it will skip middle one. If you want it to be printed twice instead, change loop condition to this:

    for(int i=0; i<(n+1)/2; i++) 

for even elements it will work as before.

Answer 2

There are multiple issues with your code.

1. You need to iterate all the elements of the array. So for loop condition should be i<(length of array).

2. There are multiple sorting algorithms to sort an array and in each of these algos you need to compare the element you are processing with other elements to decide its location in final array.

pseudo code should look like

first for loop
    second for loop 
      if element ith  > element jth   //assuming you wanted to sort in ascending format
         swap(element i and j)

I am not sharing full code since it seems like a homework problem and I suggest you should try to solve yourself.

If you see any other issue. Please update your question.

Answer 3

If you want to sort your array, you can use std::sort function. This function works on array or vector. Yours is array. Two arguments are required: the beginning of the array and the length n up to which you want the array to be sorted. Example

#include <bits/stdc++.h>
using namespace std;
 
int main()
{
    int arr[] = { 1, 5, 8, 9, 6, 7, 3, 4, 2, 0 };
    int n = sizeof(arr) / sizeof(arr[0]);
 
    sort(arr, arr + n);
 
    cout << "\nArray after sorting ";

    for (int i = 0; i < n; ++i)
        cout << arr[i] << " ";
 
    return 0;
}

This will sort in ascending order. You can add one more argument to sort in descending order:

sort(arr, arr + n, greater());