Help c++

Question

Why in this code the x is not printed and what happened?

edit:What is this random numbers?

https://code.sololearn.com/co0Br4L56MUL/?ref=app

Answer 1

James Jason Edelson Thanks for the help guys

Answer 2

Because the integer type's upper bound is limited to `2147483647`. When the result of `b + c` exceeds the upper range, the outcome will be an overflow (a.k.a. those negative values). one solution would be declaring all variables as unsigned long long to increase the acceptable range to `18446744073709551615`. Another solution would be adding a second condition inside the loop to check against integer overflow in each iteration as

while ( x < n &&
(long long)b + c <= numeric_limits<int>::max() )

Also adding the #include <limits> is mandatory at the top of the program.

Answer 3

James No, when the tutorial put a code with a "try yourself" i like to always change things in there

Answer 4

Arthur
If you ever happened to inspect the memory contents in an IDE or a Hex editor, you probably come up with a series of hexadecimal values. If you defined an integer array with 5 elements, then the compiler sets aside 20 bytes (assuming the size of int is 4 byte) of memory for the array.

int myArr[5] = {1, 2, 3, 4, 5};
int x = 8;

0xfff1011c 08 f2 a0 41 // garbage
0xfff10120 01 00 00 00 // [0]
0xfff10124 02 00 00 00 // [1]
0xfff10128 03 00 00 00 // [2]
0xfff1012c 04 00 00 00 // [3]
0xfff10130 05 00 00 00 // [4]
0xfff10134 ba f3 21 00 // garbage
0xfff10138 08 00 00 00 // x ( garbage from the array POV )

The allocated space begins from and ends to a particular address. Any value before and after those boundary are considered garbage value from the array point of view, even if they get allocated in your program by another variable immediately after the array. So, if the loop violates the array's boundary, chances are the index lands on x's value.

Answer 5

It's simple Arthur !

myArr just refers to the base address of the array or simply &myArr[0] or &myArr which gives you 0xfff10120 based on my earlier example. On the other hand, myArr[x], "dereferences" the content of the current offset from the base address indicated by range index "x", that is, *(myArr + x).
Also, range = {x | 0 <= x < array size}

Answer 6

Jason Edelson Ok,but whats is this random numbers?

Answer 7

In c++ you cant whole arrays like you can in python, your currently outputting x followed by : followed by values in array that were never assigned followed by memory pointer for array on a new line

Answer 8

Jason Edelson I know, i was testing what happening if i past the array but i forgot the myarr [x]= 42 and this happened

Answer 9

The x is printed, you can see it if you look right before the colon
0: 5059648
0x23fe301: 0
0x23fe302: 3
0x23fe303: 0

Answer 10

C++ Soldier (Babak) And what about the myarr[x]? Why is it different of myarr?

Answer 11

C++ Soldier (Babak) Can you help me in another thing?Why in this code with you put long number the output is negative?
https://code.sololearn.com/cw25FKRTCGA0/?ref=app