I tried many things, but I fell into a swamp.

When you enter an odd number, one star in the last row pops out and you try to erase it, but it's hard...

#include<iostream>
using namespace std;

int main()
{   
    int num, star, line;
    cout << "num "; 
    cin >> num;
    for (line = 0; line < num/2 1; line  )
    {
        for (star = 0; star <= line; star  ) 
        {
            cout << "*";
        }
        for (star = num/2; star > line; star--)
        {
            cout << "x";
        }
        for (star = num/2-1; star > line; star--)
        {
            cout << "x";
        }
        for (star = 0; star <= line; star  )
        {
            cout << "*";
        }
        cout << endl;
    }
}

CodePudding user response：

The problem is that the last line breaks the pattern.

This is what you get:

*xxx*
**x**
******

And from your description, I assume this is what you want:

*xxx*
**x**
*****

In all the lines before the last line, the number of x:s are odd, but in the last line, the number is even (zero). You first add three *, then zero x, then three * which makes 6 characters while the previous lines only had 5.

A direct approach at fixing it could be to count the output of *s and xs and at the end, print num minus the number printed so far *s. Example:

#include <iostream>

int main() {
    int num, star, line;

    if(!(std::cin >> num)) return 1; // error

    num |= 1; // make sure the number is odd

    for (line = 0; line < num / 2   1; line  ) {
        int output = 0; // count how many *'s and x's you've printed
        
        for (star = 0; star <= line; star  ) {
              output;
            std::cout << '*';
        }
        for (star = num / 2; star > line; star--) {
              output;
            std::cout << 'x';
        }

        for (star = num / 2 - 1; star > line; star--) {
              output;
            std::cout << 'x';
        }

        // now print  num - output  asterisks:
        for (star = 0; star < num - output; star  ) {
            std::cout << '*';
        }
        std::cout << '\n';
    }
}