File size: 856 Bytes
9438a57 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 | import java.util.*;
/**
* Fancy Binary Search
* fancy-binsearch
*
*
* Input:
* arr: A sorted list of ints
* x: A value to find
*
* Output:
* The lowest index i such that arr[i] == x, or -1 if x not in arr
*
* Example:
* >>> find_first_in_sorted([3, 4, 5, 5, 5, 5, 6], 5)
* 2
*
* @author derricklin
*/
public class FIND_FIRST_IN_SORTED {
public static int find_first_in_sorted(int[] arr, int x) {
int lo = 0;
int hi = arr.length;
while (lo < hi) {
int mid = (lo + hi) / 2; // check if this is floor division
if (x == arr[mid] && (mid == 0 || x != arr[mid-1])) {
return mid;
} else if (x <= arr[mid]) {
hi = mid;
} else {
lo = mid + 1;
}
}
return -1;
}
}
|