C ++递归函数，用于打印不起作用的标尺。

Question

I've been trying to teach myself C++ from a book. The following piece of code has been a problem, as I can't figure out what I'm doing wrong.The code is an example from the book, and yet it won't bring the same result.

The function subdivide() is supposed to use the divide and conquer method for dividing the array at midpoint and printing the character '|' there(creating an illusion of a ruler), with subsequent mid-point printing at every new line. The problem is, the final print contains only the character '|' at the end-points in all the lines, and no character is printed in the middle.

I tried to post an image, but apparently I can't.

I'll appreciate any help. Here's the C++ code:

//using recursion to subdivide a ruler
#include<iostream>
const int len=66;
const int div=6;
void subdivide(char ar[], int min,int max,int level);

int main()
{
using namespace std;
    char ruler[len];
    int i;
    for(int i=1; i<(len-2); i++)
        ruler[i]=' ';
    ruler[len-1]='\0';

    int min=0;
    int max=len-2;
    ruler[min]=ruler[max]='|';

    cout<<ruler<<endl;

    for(i=1;i<=div;i++){
        subdivide(ruler, min, max, i);
        cout<<ruler<<endl;
          for(int j=1; j<len-2; j++)
                ruler[j]=' ';
    }

return 0;
}

void subdivide(char ar[],int low,int high,int level)
{
using namespace std;
if (level==0);
    return;
int mid=(high+low)/2;
ar[mid]='|';
subdivide(ar, low, mid, level-1);
subdivide(ar, mid, high, level-1);
}

Answer 1

In your subdivide function, you have a semicolon after the if:

if (level==0);
    return;

The indentation is deceiving, and what your code is actually doing is

if (level==0);  //does nothing
return; // always returns (before modifying the ruler)

Change it to

if (level==0)    //no semicolon here
    return;

Answer 2

I got the output as shown in the pic. Is this not you want ? Remove the semicolon at if ( level == 0)