简单的递归

void recurs(argumentlist)
{
      statements1
      if (test)
            recurs(arguments)
      statements2
}

#include 
void countdown(int n);

int main()
{
    countdown(4);       // call the recursive function
    return 0;
}

void countdown(int n)
{
    using namespace std;
    cout << "Counting down ... " << n << endl;
    if (n > 0)
        countdown(n-1); // function calls itself
    cout << n << ": Kaboom!\n";
}

Counting down ... 4 ‹level 1; adding levels of recursion
Counting down ... 3 ‹level 2
Counting down ... 2 ‹level 3
Counting down ... 1 ‹level 4
Counting down ... 0 ‹level 5; final recursive call
0: Kaboom!          ‹level 5; beginning to back out
1: Kaboom!          ‹level 4
2: Kaboom!          ‹level 3
3: Kaboom!          ‹level 2
4: Kaboom!          ‹level 1

#include 
const int Len = 66;
const int Divs = 6;
void subdivide(char ar[], int low, int high, int level);
int main()
{
    char ruler[Len];
    int i;
    for (i = 1; i < Len - 2; i++)
        ruler[i] = ' ';
    ruler[Len - 1] = '\0';
    int max = Len - 2;
    int min = 0;
    ruler[min] = ruler[max] = '|';
    std::cout << ruler << std::endl;
    for (i = 1; i <= Divs; i++)
    {
        subdivide(ruler,min,max, i);
        std::cout << ruler << std::endl;
        for (int j = 1; j < Len - 2; j++)
            ruler[j] = ' '; // reset to blank ruler
    }

    return 0;
}

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

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