Question

Which XXX condition generates the following output? Not found

#include int BinarySearch(int numberList[], int element, int lowVal, int highVal) { int midVal; if (XXX) { midVal = (highVal + lowVal) / 2; if (numberList[midVal] == element) { return midVal; } else if (numberList[midVal] > element) { return BinarySearch(numberList, element, lowVal, midVal - 1); } else { return BinarySearch(numberList, element, midVal + 1, highVal); } } else { return -1; } } int main(void) { int size = 10; int numberList[size]; int element = 20; int matchPos; for (int i = 0; i < size; ++i) { numberList[i] = i; } matchPos = BinarySearch(numberList, element, 0, size - 1); if (matchPos >= 0) { printf("Found at position %d.\\", matchPos); } else { printf("Not found.\\"); } return 0; }
options:
lowVal >= highVal
lowVal == highVal
lowVal <= highVal
lowVal + highVal == 0

Answer 1

The correct condition that triggers 'Not found' in the provided BinarySearch function is 'lowVal > highVal'. This indicates the search space has been exhausted without locating the element.

Step-by-step explanation:

The condition in the BinarySearch function that generates the output 'Not found' is lowVal > highVal. The binary search algorithm requires this condition to determine when the search space has been exhausted without finding the element, indicating that the element is not in the list. If lowVal ever becomes greater than highVal, it means the search space is invalid, as the lower bound is greater than the upper bound, which should never occur in a proper subarray. Hence, the condition lowVal > highVal correctly indicates that the element is not present in the list being searched.The condition that generates the output 'Not found' is when lowVal > highVal. In the binary search algorithm, the variable lowVal represents the lowest index of the search range and highVal represents the highest index of the search range.

If lowVal is greater than highVal, it means that the search range is not valid and the element is not found in the array.In the given code, if the condition is met (lowVal>highVal), the algorithm returns -1 which indicates that the element is not found. If the condition is not met, the algorithm continues to divide the search range in half and searches for the element recursively.For example, if the array contains the elements [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] and we are searching for the element 20, the condition lowVal > highVal will be true and the output will be 'Not found'.