Given a sorted array of integers, find the starting and ending position of a given target value. Your algorithm's runtime complexity must be in the order of O(log n). If the target is not found in the array, return [-1, -1]. For example, Given [5, 7, 7, 8, 8, 10] and target value 8, return [3, 4].

Search for a Range.cpp

class Solution {
public:
    vector<int> searchRange(int A[], int n, int target) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        
        int low = low_bound(A, n, target);
        int high = high_bound(A, n, target);

        
        if(low == -1 xor high == -1) {
            if(low == -1) {
                return vector<int>{0, high - 1};
            } else {
                return vector<int>{low + 1, n - 1};
            }
        } else if(low == -1 and high == -1) {
            if(A[0] == target) {
                return vector<int>{0, n - 1};
            }
            
            return vector<int>{-1, -1};
        } else {
            return vector<int>{low + 1, high - 1};
        }
        
        
    }
    
    int low_bound(int A[], int n, int target) {
        int low = 0;
        int high = n;
        while(low < high) {
            int mid = low + (high - low) / 2;
            if(A[mid] >= target) {
                high = mid;
            } else {
                if(mid <= n - 2 && A[mid + 1] == target) {
                    return mid;
                } else {
                    low = mid + 1;
                }
            }
        }
        
        return -1;
    }

    int high_bound(int A[], int n, int target) {
        int low = 0;
        int high = n;
        while(low < high) {
            int mid = low + (high - low) / 2;
            if(A[mid] <= target) {
                low = mid + 1;
            } else {
                
                if(mid > 0 && A[mid - 1] == target) {
                    return mid;
                } else {
                    high = mid;
                }
                
            }
        }
        
        return -1;
    }
};