[Leetcode] Search for a Range

class Solution {public:    int binary_search (vector<int>& nums, int target, int start, int end) {        if (start >= end) return -1; // 因为这里没有加等号未能一次AC! Consider start = 0 and end = 1        int mid = start + (end - start) / 2;        if (nums[mid] == target) return mid;        if (nums[mid] < target) return binary_search(nums, target, mid+1, end);        else return binary_search(nums,target,start,mid);    }    vector<int> searchRange(vector<int>& nums, int target) {        vector<int> sol;        int x = binary_search(nums,target,0,nums.size());        if(x == -1) {            sol.push_back(-1);            sol.push_back(-1);        }         else {            int front = x;            int back = x;            while(front-1 >= 0 && nums[front-1] == target) front--;            while(back+1 < nums.size() && nums[back+1] == target) back++;            sol.push_back(front);            sol.push_back(back);        }        return sol;    }};