34. Search for a Range

就是二分搜索，做三遍。

1.第一遍找到第一个target

2.第二遍找到左侧的边界

3.第三遍找到右侧的边界

 

 1     public int[] searchRange(int[] nums, int target) {
 2         int[] res = new int[2];
 3         res[0] = -1;
 4         res[1] = -1;
 5         if(nums == null || nums.length == 0) {
 6             return res;
 7         }
 8         int low = 0;
 9         int high = nums.length - 1;
10         int mid = 0;
11         boolean found = false;
12         while(low <= high) {
13             mid = low + (high - low) / 2;
14             if(nums[mid] == target) {
15                 found = true;
16                 break;
17             } else if(nums[mid] > target) {
18                 high = mid - 1;
19             } else {
20                 low = mid + 1;
21             }
22         }
23         if(found == true) {
24             int l = mid;
25             int r = nums.length - 1;
26             int m = 0;
27             while(l <= r) {
28                 m = l + (r - l) / 2;
29                 if(nums[m] == target) {
30                     l = m + 1;
31                 } else {
32                     r = m - 1;
33                 }
34             }
35             res[1] = r;
36             l = 0; 
37             r = m;
38             while(l <= r) {
39                 m = l + (r - l) / 2;
40                 if(nums[m] == target)  {
41                     r = m - 1;
42                 } else {
43                     l = m + 1;
44                 }
45             }
46             res[0] = l;
47         }
48         return res;
49     }

 

posted @ 2016-02-26 10:10  warmland  阅读(122)  评论(0)  编辑  收藏  举报