SearchRange

最新推荐文章于 2024-08-11 17:43:07 发布

转载最新推荐文章于 2024-08-11 17:43:07 发布 · 179 阅读

0 ·

CC 4.0 BY-SA版权

原文链接：http://www.cnblogs.com/CoalberSoft/p/4803554.html

查找range相比简单版的二分查找，考察的点主要还是逻辑条件的判断以及边界值的判断

使用这种方式，需要注意的三个细节，

1：是index的默认值为-1。 -1为默认的返回值，即失败时返回-1

2：判断条件， num[mid] >= target 很好的覆盖了将end缩短的条件

3：index的赋值，遍历一遍后，要保存index，还必须符合另外一个 nums[mid] == target的条件



 1 public class SearchRange {
 2     protected static final Logger LOGGER = LoggerFactory.getLogger(SearchRange.class);
 3 
 4     public int[] searchRange(int[] nums, int target) {
 5         int leftBound = findLeft(nums, 0, nums.length - 1, target);
 6         int rightBound = findRight(nums, 0, nums.length - 1, target);
 7         return new int[] { leftBound, rightBound };
 8     }
 9 
10     public int findLeft(int[] nums, int start, int end, int target) {
11         int index = -1; // default code to the fail case
12         while (end >= start) {
13             int mid = (end - start) / 2 + start;
14             if (nums[mid] >= target) {
15                 end = mid - 1;
16             } else {
17                 start = mid + 1;
18             }
19 
20             if (nums[mid] == target) {
21                 index = mid;
22             }
23         }
24         return index;
25     }
26 
27     public int findRight(int[] nums, int start, int end, int target) {
28         int index = -1; // default code to the fail case
29         while (end >= start) {
30             int mid = (end - start) / 2 + start;
31             if (nums[mid] <= target) {
32                 start = mid + 1;
33             } else {
34                 end = mid - 1;
35             }
36 
37             if (nums[mid] == target) {
38                 index = mid;
39             }
40         }
41         return index;
42 
43     }
44 
45         public static void main(String[] args) {
46         SearchRange searchRange = new SearchRange();
47         LOGGER.info("{}", searchRange.searchRange(new int[] { 2, 2 }, 2));
48 
49     }
50 }

转载于:https://www.cnblogs.com/CoalberSoft/p/4803554.html