Ziezi - 4 months ago 34

C Question

This is the code:

`char binarySearch(unsigned int target, int* primes, unsigned int size){`

int* ptrToArray = primes;

unsigned int first = 0;

unsigned int last = size;

while (first <= last){

unsigned int middle = first + (last - first) / 2;

printf("first: %d, last: %d, middle: %d\n", first, last , middle);

if (ptrToArray[middle] == target){

return 1;

}

if (ptrToArray[middle] < target){

first = middle + 1;

}else{

last = middle - 1;

}

}

return 0;

}

This is the output:

I've been staring at that peace of code for more than one should and still can't figure out where is the flaw.

Answer

If `middle`

is `0`

, as near the end of your debug output, the statement

```
last = middle - 1
```

causes an integer overflow; the conditions have to be reworked a bit.