[Leetcode] search for a Range

The idea is to search for the left and right boundaries of target via two binary searches. Well, some tricks may be needed. Take a look at this link :-)

The code is rewritten as follows.

 1 class Solution { 2 public: 3     vector<int> searchRange(vector<int>& nums, int target) { 4         int l = left(nums, target); 5         if (l == -1) return {-1, -1}; 6         return {l, right(nums, target)}; 7     } 8 private: 9     int left(vector<int>& nums, int target) {10         int n = nums.size(), l = 0, r = n - 1;11         while (l < r) {12             int m = l + ((r - l) >> 1);13             if (nums[m] < target) l = m + 1;14             else r = m;15         }16         return nums[l] == target ? l : -1;17     }18     int right(vector<int>& nums, int target) {19         int n = nums.size(), l = 0, r = n - 1;20         while (l < r) {21             int m = l + ((r - l + 1) >> 1); 22             if (nums[m] > target) r = m - 1;23             else l = m;24         }25         return r;26     }27 }; 

 

[Leetcode] search for a Range