double free or corruption (!prev) error in c program

double *ptr = malloc(sizeof(double *) * TIME);
/* ... */
for(tcount = 0; tcount <= TIME; tcount++)
                         ^^

• You’re overstepping the array. Either change <= to < or alloc SIZE + 1 elements
• Your malloc is wrong, you’ll want sizeof(double) instead of sizeof(double *)
• As ouah comments, although not directly linked to your corruption problem, you’re using *(ptr+tcount) without initializing it

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• Just as a style note, you might want to use ptr[tcount] instead of *(ptr + tcount)
• You don’t really need to malloc + free since you already know SIZE