LeetCode Search for a Range

思路：
二分法找到nums中得target，然后左右扩展，返回坐标。

class Solution {
public:
    vector<int> searchRange(vector<int>& nums, int target) {
        vector<int> res = {-1, -1};
        int i = 0, j = nums.size() - 1;
        while(i <= j) {
            int mid = (i + j)/2;
            if(nums[mid] == target) {
                int left = mid - 1;
                int right = mid + 1;
                while(left >= 0 && nums[left] == target) left--;
                while(right <= j && nums[right] == target) right++;
                res[0] = left + 1;
                res[1] = right - 1;
                return res;
            }else if(nums[mid] < target) {
                i = mid + 1;
            }else {
                j = mid - 1;
            }
        }
        return res;
    }
};