Recursively printing out the sections and subsections of an outline - c

Question

Recursion is the one thing I have loads of trouble with. For this assignment we are supposed to print out an outline of sections and sub-sections. Take the following as an example.
Section 1
Section 1.A
Section 1.A.1
Section 1.A.2
Section 1.B
Section 1.B.1
Section 1.B.2
Section 2
Section 2.A
Section 2.A.1
Section 2.A.2
Section 2.B
Section 2.B.1
Section 2.B.2
This example has a depth of 3 and height of 2.
Here is my code thus far, which doesn't come anywhere near the correct output.
void printDepth(int depth, int width, int minusDepth, int minusWidth) {
int i = 0;
if(depth == 0)
printf("Section XX\n");
else {
printf("\t");
printDepth(depth -1, width, minusDepth, minusWidth);
}
}
Here is the call from main()
int minusDepth = 0;
int minusWidth = 0;
printDepth(depth, width, minusDepth, minusWidth);
However, for a depth = 4 and width = 5 this only prints out:
\t\t\t\tSection XX
I'm really not sure how to proceed. Recursion is the bane of my existence.

Answer 1

You need a loop that prints the sections at the current depth and executes height (which I call width instead) recursions. You also need to pass a string containing the current prefix of the section string.
#include <stdio.h>
#include <assert.h>
#include <math.h>
#define MAX_DEPTH 100
#define MAX_WIDTH 99 // NOTE: if you increase this then section's decl in printDepth needs to be updated too
void printDepth_r(int currDepth, int depth, int width, char *section, char *sub)
{
if (currDepth == depth) // recursion base case
return;
for (int i = 0; i < width; ++i)
{
// TODO: write to sub the subsection determined by (currDepth, width)
fprintf(stdout, "%*sSection %s\n", currDepth * 2, "", section);
// TODO: append "." to sub for descendant recursions
printDepth_r(currDepth + 1, depth, width, section, sub + /* TODO: num chars written to sub */);
}
}
int printDepth(int depth, int width)
{
char section[MAX_DEPTH * (2 + 1) + 1]; // NOTE: 2 == 1 + (int) (log(99) / log(10));
assert(sizeof(section) >= MAX_DEPTH * (1 + (int) (log(MAX_WIDTH) / log(10)) + 1) + 1);
if (depth > MAX_DEPTH || width > MAX_WIDTH)
return -1;
printDepth_r(0, depth, width, section, section);
return 0;
}
int main(int argc, char **argv)
{
printDepth(3, 2);
return 0;
}
Note that we pass the same values of depth, width and section to all of our recursions. So, if we wanted to reduce the amount of stack space the recursion eats at every level, then we could pull these out into a structure and pass 1 struct pointer to these 3 constants instead. Or, even better, we could store these values in thread local storage. Either way would allow deeper recursions before overflowing your stack.

Answer 2

#include <stdio.h>
void printDepth(int deep, int depth, int height, char *table) {
if(deep == depth)
return ;
int i, j;
char bak = table[deep];
for(i = 0; i < height; ++i){
printf("%*s%s", deep*2, "", "Section ");
for(j = 0; j <= deep; ++j){
if(j)
putchar('.');
putchar(table[j]);
}
putchar('\n');
printDepth(deep+1, depth, height, table);
table[deep]++;
}
table[deep] = bak;//restore
}
int main(void){
char table[] = "1A1";//Effective range up to 1-9 and A-Z
printDepth(0, 3, 2, table);
return 0;
}