alternative for STL - lower_bound, upper_bound, binary_search

binary_search(short).cpp

template<typename T>
bool binary_search(T *arr, T *end, const T& x) {
    return *lower_bound(arr, end, x) == x;
}

binary_search.cpp

template<typename T>
bool binary_search(T *arr, T *end, const T& key) {
    int l = 0, r = (int)(end - arr) - 1;
    while (l <= r) {
        int mid = (l + r) / 2;
        if (arr[mid] < key) {
            l = mid + 1;
        }
        else {
            r = mid - 1;
        }
    }
    return arr[l] == key;
}

lower_bound.cpp

template<typename T>
T* lower_bound(T *arr, T *end, const T& key) {
    int l = 0, r = (int)(end - arr) - 1;
    while (l <= r) {
        int mid = (l + r) / 2;
        if (arr[mid] < key) {
            l = mid + 1;
        }
        else {
            r = mid - 1;
        }
    }
    return arr + l;
}

upper_bound.cpp

template<typename T>
T* upper_bound(T *arr, T *end, const T& key) {
    int l = 0, r = (int)(end - arr) - 1;
    while (l <= r) {
        int mid = (l + r) / 2;
        if (key < arr[mid]) {
            r = mid - 1;
        }
        else {
            l = mid + 1;
        }
    }
    return arr + l;
}