如何在 C++ 中打印等腰三角形

Question

I'm trying to create an isosceles triangle with '*' symbol from user's input in C++.

For example, with user's input of 5, I must get:

*
**
***
****
*****
****
***
**
*

I'm getting only:

*
**
***
****
*****

My c++ code:

void askData(int &n){
    cout<<"Enter a number: ";
    cin>>n;
}

void print(int A){
    for(int j=1;j<=A;j++)
    cout<<"*";
    cout<<endl;
}

void createIsoscTriangle(int n){

    for(int i=1;i<=n;i++){
    print(i);
}

int main()
{
    int n;
    askData(n);
    createIsoscTriangle(n);
    return 0;
}

How can I get the correct form of the isosceles triangle?

Answer 1

The pattern of stars is 1 , 2 , 3 , ... , n , n - 1 , n - 2 , ... , 1. as Brian mentioned in the comments. So, Numbers of stars for each line would be n - abs(n - i) , where abs is the absolute value of n - i , and that should work for any n not just 5 .

I've modified your createIsoscTriangle function to be the following:

void createIsoscTriangle(int n) {

    for(int i = 1; i <= n * 2 - 1; i++)
        print(n - abs(n - i)); 
}

Let's try it for n = 5 . It would print the figure you mentioned.

*
**
***
****
*****
****
***
**
*

Answer 2

You only print sequence 1 2 3 4 5 . You also need a loop which would count down.

void createIsoscTriangle(int n) {
    for(int i = 1; i <= n; i++)
      print(i);
    for(int i = n-1; i >= 1; i--)
      print(i);
}