Prentice.Hall.Introduction.to.Java.Programming,.Brief.Version.9th.(2014).[sharethefiles.com]

6.10 Searching Arrays 247
key is 11
low
mid
high
key 50
key 7
key 11
[0] [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12]
list 2 4 7 10 11 45 50 59 60 66 69 70 79
low mid high
[0] [1] [2] [3] [4] [5]
list 2 4 7 10 11 45
low mid high
[3] [4] [5]
list 10 11 45
FIGURE 6.10
comparison.
Binary search eliminates half of the list from further consideration after each
public static int binarySearch(
int[] list, int key) {
int low = 0;
int high = list.length - 1;
int mid = (low + high) / 2;
if (key < list[mid])
high = mid - 1;
else if (key == list[mid])
return mid;
else
low = mid + 1;
public static int binarySearch(
int[] list, int key) {
int low = 0;
int high = list.length - 1;
while (high >= low) {
int mid = (low + high) / 2;
if (key < list[mid])
high = mid - 1;
else if (key == list[mid])
return mid;
else
low = mid + 1;
}
}
}
return -1;
// Not found
(a) Version 1
(b) Version 2
FIGURE 6.11 Binary search is implemented incrementally.
indicate that the key matches list[0]. A good choice is to let the method return –low – 1
if the key is not in the list. Returning –low – 1 indicates not only that the key is not in the list,
but also where the key would be inserted.
The complete program is given in Listing 6.7.
LISTING 6.7
BinarySearch.java
1 public class BinarySearch {
2 /** Use binary search to find the key in the list */
3 public static int binarySearch(int[] list, int key) {
4 int low = 0;
5 int high = list.length - 1;
6
7
8
while (high >= low) {
int mid = (low + high) / 2;
9 if (key < list[mid])
10 high = mid - 1;
11 else if (key == list[mid])
first half