do while for array in c - c

Question

i work for a question that generate random number and sort in array, then display numbers from biggest to smallest.
here is my code:
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define SIZE 40
int main()
{
int array[SIZE];
int inner, outter, temp, i;
srand((unsigned)time(NULL));
//do... while to assign array value
i=0;
do{
array[i] = (int)((rand()%101)+1);
i++;
}while(i<SIZE);
puts("Original array:");
for(outter=0; outter<SIZE-1;outter++){
printf("%d\t", array[outter]);
}
//bubble sort
for(outter=0; outter<SIZE-1;outter++){
for(inner=outter+1; inner<SIZE; inner++ ){
if(array[outter] > array[inner]){
temp = array[outter];
array[outter] = array[inner];
array[inner] = temp;
}
}
}
puts("\n");
puts("Sorted array:");
printf("i= %d\n",i);
printf("%d\n", array[39]);
for(outter=0; outter<SIZE;outter++){
printf("%d\t", array[outter]);
}
puts("\n");
for(outter=SIZE-1; outter>0;outter--){
printf("%d\t", array[outter]);
}
puts("\n");
// try using do while loop to display reverse number from biggest to smallest numbers
do{
printf("i= %d\n", i-1);
i--;
}while(i>-1);
}
when i used do while for displaying reverse array number, my code goes crush.
However, i display the value the "i" that used for looping array, it displayed from 39 to -1. I don not why i have -1 for "i" value since i set "i>-1".

Answer 1

TL;DR: Either change your printf to this: printf("i= %d\n", i); or change your while loop to while(i > 0);. Either way, it should fix your problem.
A do while loop does the action in the curly braces and then checks the condition. I'm not quite understanding your question, but it seems to me that it's printing -1 because it's doing first, then checking the condition. Furthermore, you're using i - 1 in your printf function (which is probably where you've confused yourself the most).
EDIT: To be even more explicit about the while loop, the problem is that your condition is (i > -1). That means that when you reach 0, your code will check: is 0 greater than -1?. It will return true and then move on the i = -1 where it prints -1. Then it reaches the while condition once more where it sees that -1 is not greater than -1 which is when the code terminates.

Answer 2

Your main problem is probably the starting value for i.
After the first do ... while loop it equals 40 when the condition fails.
Therefore you could make things a lot easier if you adjust your starting value for the second loop:
i--; // or i = SIZE-1;
do{
printf("i= %d\n", i);
i--;
} while (i >= 0);
Then you don't have any headache by shifting your values by one and can just use the values you want.
If you insist on doing it the way you did, then check the limits...
do{
printf("i= %d\n", i-1); // last value to be printed is 0 ==> i == 1
i--; // The last wanted value of i now is 0.
} while (i>0); // Stop if we reach last wanted value