I have the following binary search method and the following driver code. Both of the values I search for show in the output are present in the array.
Search Method
//Method for binary search. This method will also cut our array
public static int binarySearch(int[] nums, int x) {
//Bounds
int l = 0, r = nums.length - 1;
//While the size of the array is not 1
while (l <= r) {
//Middle element
int m = l + (r - 1) / 2;
//If our element is the middle
if (nums[m] == x) return m;
//If x is greater, cut to right half
else if (x > nums[m]) l = m + 1;
//Else, ignore right half
else r = m - 1;
}
//If we didn't find the element
return -1;
}
Driver code and output
public class searcher {
public static void main(String[] args) {
/* Initialize a new scanner for user input, initialize random for the
computer to pick a number */
Scanner s = new Scanner(System.in);
//Variable for user input
int guess;
//Do-while loop
do {
System.out.println("Enter a number to search for (0 to quit): ");
//Get the user's guess
guess = s.nextInt();
//Search for the guess in the array of numbers
int i = binarySearch(nums, guess);
System.out.println(i);
//If the number is not found
if (i == -1) {
System.out.println("Your number does not occur in this list.");
}
//If it is
else {
System.out.println("Your number occurs at position " + i);
}
} while (guess != 0);
}
}
/*
Output
Enter a number to search for (0 to quit):
1
1
Your number occurs at position 1
Enter a number to search for (0 to quit):
90
<------- Program doesn't stop running from here...? */
I'm expecting to get an output for the index of the number entered if its found, and if not, the method should return -1 so I can print not found
You are subtracting 1 twice.
r = nums.length - 1;
and then
int m = l + (r - 1) / 2;
should be
int m = l + (r - l) / 2;