34. Find First and Last Position of Element in Sorted Array

对mid两边进行binary search 得出边界

 

 

 

 1 class Solution {
 2     public int[] searchRange(int[] nums, int target) {
 3         int[] res = {-1, -1};
 4         if(nums.length == 0) return res;
 5         int[] bi = biSearch(nums, target, 0, nums.length - 1);
 6         if(bi[0] == Integer.MAX_VALUE) {
 7             return res;
 8         }else {
 9             return bi;
10         }
11         
12     }
13     
14     public int[] biSearch(int[] nums, int target, int lo, int hi) {
15         int[] res = {Integer.MAX_VALUE, Integer.MIN_VALUE};
16         
17         while(lo <= hi) {
18             int mid = lo + (hi - lo)/2;
19             if(nums[mid] == target) {
20                 res[0] = Math.min(mid, biSearch(nums, target, lo, mid-1)[0]);
21                 res[1] = Math.max(mid, biSearch(nums, target, mid+1, hi)[1]);
22                 return res; //因为是recursive的 所以在这边就可以返回
23             }else if(nums[mid] < target) {
24                 lo = mid + 1;
25             }else {
26                 hi = mid - 1;
27             }
28         }
29         return res;
30     }
31 }

 

posted @ 2018-09-10 06:14  jasoncool1  阅读(95)  评论(0)  编辑  收藏  举报