Array is printing with weird question mark symbols when printing fibonacci sequences - c

Question

When printing each Fibonacci sequence the first couple of sequences print in weird symbols or not at all if printing more than 8 sequences.
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>
//n=amount of numbers in the series to compute, seq=array to store series
void fibonacci(int n, int* seq){
// Complete this function
int i;
seq[0] = 0;
seq[1] = 1;
for(i = 2; i <= n; i++){
seq[i] = seq[i-2] + seq[i-1];
}
}
int main(){
int n;
//n, amount of series to compute
scanf("%d",&n);
//initialize array to 1, using malloc/calloc
int *seq = malloc(1 * sizeof(*seq));
int i;
for(i = 1; i <= n; i++){
//recompute the whole series
fibonacci(i, seq);
//print array
int j;
for(j = 0; j < i; j++)/* complete code */
printf("%d ", seq[j]);
//resize array, with realloc
int newSize=i+1;
int *seq = realloc(seq, newSize);
printf("\n");
}
//free array
return 0;
}
Output:
"7Y��yb�=
Um�*/E�o 1 1 2 3 5 8 13
0 1 1 2 3 5 8 13 21
0 1 1 2 3 5 8 13 21 34
0 1 1 2 3 5 8 13 21 34 55
0 1 1 2 3 5 8 13 21 34 55 89
0 1 1 2 3 5 8 13 21 34 55 89 144
0 1 1 2 3 5 8 13 21 34 55 89 144 233
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584 4181
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584 4181 6765
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584 4181 6765 10946

Answer 1

There are different problems in your code:
In your fibonacci() function, you iterate using i <= n, but inside the loop, you assign to seq[i]. When i = n, this becomes a problem: you're accessing one cell out of the array.
You are getting n from user input, but then doing int *seq = malloc(1 * sizeof(*seq)). You are only allocating space for one element, not n. You should do malloc(n * sizeof(*seq)) instead.
Not really an error, but inside the first for loop in your main, you're both re-defining and re-allocating the seq array with int *seq = realloc(...). That is not needed at all. Your array is already n cells big, so there is no need to reallocate it each time. You can use it as is.
Not really an error, but there is no need to recompute the series each time. You can compute it only once and then partially print it on each row without a problem.
Also, IMPORTANT! Using int to hold numbers of the Fibonacci sequence is only good until you reach n = 47. More than that, and your next element will overflow the maximum positive value that an int can hold, turning negative, and invalidating the rest of the calculations too. I would suggest you to use long long unsigned int instead, which would be good up to n = 94 (assuming 64 bits). Ultimately, you should check the value of n before calculating the Fibonacci sequence to avoid an overflow.
Here's a better version of your code with those problems fixed:
void fibonacci(int n, int* seq) {
int i;
seq[0] = 0;
seq[1] = 1;
for(i = 2; i < n; i++)
seq[i] = seq[i-2] + seq[i-1];
}
int main() {
int *seq;
int n, i, j;
scanf("%d",&n);
// Allocate enough space for n elements:
seq = malloc(n * sizeof(*seq));
// Compute the whole series once:
fibonacci(n, seq);
// Print partial series on each row:
for(i = 1; i <= n; i++) {
for(j = 0; j < i; j++)
printf("%d ", seq[j]);
printf("\n");
}
free(seq);
return 0;
}