C For Loop Floyd's Triangle but different? - c

Question

I need help on how to do a Flyod's Triangle style but instead of input value in rows, the triangle is based on the input value as a whole.
instead of;
Enter a number: 9
1
2 3
4 5 6
7 8 9 10
11 12 13 14 15
16 17 18 19 20 21
22 23 24 25 26 27 28
29 30 31 32 33 34 35 36
37 38 39 40 41 42 43 44 45
it should be
Enter a number: 9
1
23
456
789
here is my code
#include <stdio.h>
int main() {
int rows, i, j, number = 1;
printf("Enter a number: ");
scanf("%d", &rows);
for (i = 1; i <= rows; i++) {
for (j = 1; j <= i; ++j) {
printf("%d ", number);
++number;
}
printf("\n");
}
return 0;
}

Answer 1

To easily structure your output you might retain a row counter; in contrast to your code it only serves to determine how many columns we need per row, so:
for(size_t row = 1; ; ++row) // note: no condition; we'll break from within!
{
for(size_t col = 0; col < row; ++col)
{
// we'll print the values here!
}
}
This is the basic structure how to define rows and colums.
Now you'll input before this loop the target number up to which to output values, and you'll have a separate counter running up to the number just received by the user, i.e.:
int number;
if(scanf("%d", &number) != 1) // test to catch invalid input, though it does not
// catch all types of, e.g. for 77xyz the value 77
// will be scanned!
{
// TODO: error message!
}
else if(number < 0)
{
// again invalid input!
// TODO: error message
}
else if(number == 0):
{
// special case, don't output anything
}
else
{
int counter = 1;
// now our loops:
for(size_t row = 1; ; ++row)
{
for(size_t col = 0; col < row; ++col)
{
printf("%.2d ", counter);
// .2 is optional, it serves for better alignment of the output
// though fit ails for number > 99; you might calculate *before*
// this nested loop how many indentation you actually need...
// and now we check if we need to stop!
if(counter == number)
{
// as within main, we can just return; maybe add another
// newline before:
return 0;
}
++counter; // go on with next number
}
putchar('\n');
}
}
Note how the loop counters don't have any influence on stopping the output, only our explicit counter variable has.
Note, too, that above code is untested, so if you find a bug, please fix yourself.

Answer 2

#include <stdio.h>
int main() {
int max_num, i, j, number = 1;
printf("Enter a number: ");
scanf("%d", &max_num);
for (i = 1; 1; i++) {
for (j = 1; j <= i; ++j) {
printf("%d ", number);
++number;
if (number > max_num) {
return 0;
}
}
printf("\n");
}
return 0;
}